Optical communication apparatus, optical communication system and optical communication method

ABSTRACT

An optical communication device includes an optical switch that outputs an optical signal input from one of a plurality of transmission lines to another transmission line among the plurality of transmission lines, a monitoring unit that relays an optical signal in a transmission line on a side where the optical signal is output from the optical switch, a blocking unit that blocks transmission of an optical signal output from the monitoring unit, a wavelength controller that allocates a wavelength and the like that are a wavelength, a time, a polarization, a mode, a code, a frequency, a core, a core wire, or a combination thereof to an optical signal of a subscriber device via the monitoring unit, and an optical switch controller that controls the optical switch such that the optical signal input from the transmission line to the optical switch is output to the another transmission line, and cancels the blocking by the blocking unit.

TECHNICAL FIELD

The present invention relates to an optical communication device, anoptical communication system, and an optical communication method.

BACKGROUND ART

A network that provides a high-speed Internet by using fiber to the home(FTTH) or a mobile service is inefficient in terms of operation becausethe network is independently constructed for each service. Therefore, anoptical access system that accommodates a plurality of services with onedevice has been proposed (refer to, for example, Non Patent Literature1). In order to realize an optical access system capable ofaccommodating multiple services, a passive optical network (PON) or awavelength division multiplexing (WDM)-PON using a plurality ofwavelengths has been standardized by the International TelecommunicationUnion-Telecommunication Standardization Sector (ITU-T) (refer to, forexample, Non Patent Literature 2).

On the other hand, an existing optical access system includes a deviceon a subscriber side and a terminal device on a station side, andcommunication between the devices is connected to a higher network suchas a core network via the terminal device. The device on the subscriberside is, for example, an optical network unit (ONU). Connection to thecore network is performed via the terminal device in a device on thestation side. The terminal device is, for example, an optical lineterminal (OLT). In optical access connected to the core network throughpacket exchange, a process of adding or deleting user information ordestination information to or from a signal, a routing process, and thelike are performed on the signal. When user information or destinationinformation is added or deleted, an optical signal may be convertedtemporarily into an electrical signal. In this case, a certain delayoccurs in communication. When an amount of data increases, signals arestored in a buffer, and priority control or the like may be performed.This further increases the delay. When the delay increases, the qualityof an optical service greatly decreases. Therefore, it is important toreduce the delay as much as possible.

In order to improve quality of an optical service and provide variousservices in an optical access network, delays that occur need to bereduced. By using an optical switch or the like capable of performingprocessing such as routing without converting an optical signal into anelectrical signal, a delay can be greatly reduced.

CITATION LIST Non Patent Literature

-   Non Patent Literature 1: “ITU-T G.983.3”, International    Telecommunication Union, 2001-   Non Patent Literature 2: “ITU-T G.989.1”, International    Telecommunication Union, 2013

SUMMARY OF INVENTION Technical Problem

Incidentally, in routing using an optical switch, it is necessary to seta path of an optical signal according to a transfer destination on apath to a communication destination of a device on a subscriber side,and further to perform setting (wavelength or the like) of a transceiverof the device on the subscriber side. In a case where routing ofmulticast, broadcast, or return communication using an optical switch isapplied to optical access, it is desired to reduce the number of portsused for routing in order to connect many devices.

In view of the above circumstances, an object of the present inventionis to provide a technique capable of relaying an optical signal to adestination while reducing the number of ports to be used.

Solution to Problem

According to an aspect of the present invention, there is provided anoptical communication device including an optical switch that outputs anoptical signal input from one of a plurality of transmission lines toanother transmission line among the plurality of transmission lines; amonitoring unit that relays an optical signal in a transmission line ona side where the optical signal is output from the optical switch; ablocking unit that blocks transmission of an optical signal output fromthe monitoring unit; a wavelength controller that allocates a wavelengthand the like that are a wavelength, a time, a polarization, a mode, acode, a frequency, a core, a core wire, or a combination thereof to anoptical signal of a subscriber device via the monitoring unit; and anoptical switch controller that controls the optical switch such that theoptical signal input from the transmission line to the optical switch isoutput to the another transmission line, and cancels the blocking by theblocking unit.

According to another aspect of the present invention, there is providedan optical communication device including a first optical switch thatoutputs an optical signal input from one of a plurality of transmissionlines to another transmission line among the plurality of transmissionlines; a second optical switch that is cascade-connected to the firstoptical switch; a monitoring unit that relays an optical signal in atransmission line on a side where the optical signal is output from thefirst optical switch or the second optical switch;

-   -   a blocking unit that blocks transmission of an optical signal        output from the monitoring unit; a wavelength controller that        allocates a wavelength and the like that are a wavelength, a        time, a polarization, a mode, a code, a frequency, a core, a        core wire, or a combination thereof to an optical signal of a        subscriber device; and an optical switch controller that        controls the first optical switch and the second optical switch        such that the optical signal input from the transmission line to        the first optical switch is output to the another transmission        line, and cancels the blocking by the blocking unit.

According to still another aspect of the present invention, there isprovided an optical communication system including a plurality ofsubscriber devices; and the above optical communication device.

According to still another aspect of the present invention, there isprovided an optical communication method executed by an opticalcommunication device, including an optical switch step of outputting anoptical signal input from one of a plurality of transmission lines toanother transmission line among the plurality of transmission lines; amonitoring step of relaying an optical signal in a transmission line ona side where the optical signal is output from the optical switch; ablocking step of blocking transmission of an optical signal output inthe monitoring step; a wavelength control step of allocating awavelength and the like that are a wavelength, a time, a polarization, amode, a code, a frequency, a core, a core wire, or a combination thereofto an optical signal of a subscriber device; and an optical switchcontrol step of controlling the optical switch such that an opticalsignal input from the transmission line to the optical switch is outputto the another transmission line, and canceling the blocking.

Advantageous Effects of Invention

According to the present invention, it is possible to relay an opticalsignal to a destination while reducing the number of ports to be used.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a basic configuration example of anoptical communication system according to an embodiment.

FIG. 2 is a diagram illustrating an example of an optical SW accordingto a basic configuration.

FIG. 3 is a diagram illustrating an example of an optical SW accordingto a basic configuration.

FIG. 4 is a diagram illustrating an example of an optical SW accordingto a basic configuration.

FIG. 5 is a diagram illustrating an example of an optical SW accordingto a basic configuration.

FIG. 6 is a diagram illustrating an example of an optical SW accordingto a basic configuration.

FIG. 7 is a diagram illustrating an example of routing before wavelengthchange in the optical SW according to the basic configuration.

FIG. 8 is a diagram illustrating an example of routing after wavelengthchange in the optical SW according to the basic configuration.

FIG. 9 is a diagram illustrating an example of an optical SW accordingto a basic configuration.

FIG. 10 is a diagram illustrating an example of an optical SW accordingto a basic configuration.

FIG. 11 is a diagram illustrating an example of an optical SW accordingto a basic configuration.

FIG. 12 is a diagram illustrating an example of an optical SW accordingto a basic configuration.

FIG. 13 is a diagram illustrating an example of an optical SW accordingto a basic configuration.

FIG. 14 is a diagram illustrating an example of an optical SW accordingto a basic configuration.

FIG. 15 is a diagram illustrating an example of an optical SW accordingto a basic configuration.

FIG. 16 is a diagram illustrating an example of an access topologyaccording to a basic configuration.

FIG. 17 is a diagram illustrating an example of an access topologyaccording to a basic configuration.

FIG. 18 is a diagram illustrating an example of an access topologyaccording to a basic configuration.

FIG. 19 is a diagram illustrating an example of an access topologyaccording to a basic configuration.

FIG. 20 is a diagram illustrating an example of an access topologyaccording to a basic configuration.

FIG. 21 is a diagram illustrating an example of an access topologyaccording to a basic configuration.

FIG. 22 is a diagram illustrating an example of an access topologyaccording to a basic configuration.

FIG. 23 is a diagram illustrating an example of an access topologyaccording to a basic configuration.

FIG. 24 is a diagram illustrating an example of an access topologyaccording to a basic configuration.

FIG. 25 is a diagram illustrating an example of an access topologyaccording to a basic configuration.

FIG. 26 is a diagram illustrating an example in which scalability of anoptical SW according to a basic configuration is required.

FIG. 27 is a diagram illustrating an example in which scalability of anoptical SW according to a basic configuration is required.

FIG. 28 is a diagram illustrating an example in which scalability of anoptical SW according to a basic configuration is required.

FIG. 29 is a diagram illustrating a configuration example of a twin-coresubscriber device according to a basic configuration.

FIG. 30 is a diagram illustrating a configuration example of a twin-coresubscriber device according to a basic configuration.

FIG. 31 is a diagram illustrating a configuration example of asingle-core subscriber device according to a basic configuration.

FIG. 32 is a diagram illustrating a configuration example of asingle-core subscriber device according to a basic configuration.

FIG. 33 is a diagram illustrating a configuration example of amonitoring unit according to a basic configuration.

FIG. 34 is a diagram illustrating a configuration example of amonitoring unit according to a basic configuration.

FIG. 35 is a diagram illustrating a configuration example of amonitoring unit according to a basic configuration.

FIG. 36 is a diagram illustrating a configuration example of amonitoring unit according to a basic configuration.

FIG. 37 is a diagram illustrating a configuration example of amonitoring unit according to a basic configuration.

FIG. 38 is a diagram illustrating a configuration example of an opticalaccess system according to a configuration example.

FIG. 39 is a diagram illustrating an example of a SW connection tableaccording to the same configuration example.

FIG. 40 is a diagram illustrating an example of a user wavelength tableaccording to the same configuration example.

FIG. 41 is a diagram illustrating an example of an inter-stationwavelength table according to the same configuration example.

FIG. 42 is a flowchart illustrating an initial setting process of theoptical access system according to the configuration example.

FIG. 43 is a diagram illustrating a configuration example of an opticalaccess system according to a first configuration example.

FIG. 44 is a diagram illustrating a configuration example of an opticalaccess system according to a second configuration example.

FIG. 45 is a diagram illustrating a configuration example of an opticalaccess system according to a third configuration example.

FIG. 46 is a diagram illustrating a configuration example of an opticalaccess system according to a fourth configuration example.

FIG. 47 is a diagram illustrating a configuration example of an opticalaccess system according to a fifth configuration example.

FIG. 48 is a diagram illustrating a configuration example of an opticalaccess system according to a sixth configuration example.

FIG. 49 is a diagram illustrating a configuration example of an opticalaccess system according to a seventh configuration example.

FIG. 50 is a diagram illustrating a configuration example of an opticalaccess system according to an eighth configuration example.

FIG. 51 is a diagram illustrating a configuration example of an opticalaccess system according to a ninth configuration example.

FIG. 52 is a diagram illustrating a configuration example of an opticalaccess system according to a tenth configuration example.

FIG. 53 is a diagram illustrating a configuration example of an opticalaccess system according to an eleventh configuration example.

FIG. 54 is a diagram illustrating a configuration example of an opticalaccess system according to a twelfth configuration example.

FIG. 55 is a diagram illustrating a configuration example of an opticalaccess system according to a thirteenth configuration example.

FIG. 56 is a diagram illustrating a configuration example of an opticalaccess system according to a fourteenth configuration example.

FIG. 57 is a diagram illustrating a configuration example of an opticalaccess system according to a fifteenth configuration example.

FIG. 58 is a diagram illustrating a configuration example of an opticalaccess system according to a sixteenth configuration example.

FIG. 59 is a diagram illustrating a configuration example of an opticalaccess system according to the sixteenth configuration example in a casewhere an electrical processing unit multiplexes signals.

FIG. 60 is a diagram illustrating a configuration example of an opticalaccess system according to a seventeenth configuration example.

FIG. 61 is a diagram illustrating a configuration example of an opticalGW in an optical access system according to a first embodiment.

FIG. 62 is a diagram illustrating a configuration example of an opticalGW in an optical access system according to a second embodiment.

FIG. 63 is a diagram illustrating a configuration example of an opticalGW in an optical access system according to a third embodiment.

FIG. 64 is a diagram illustrating a configuration example of an opticalGW in an optical access system according to a fourth embodiment.

FIG. 65 is a diagram illustrating a configuration example of an opticalGW in an optical access system according to a fifth embodiment.

FIG. 66 is a diagram illustrating another aspect of scalability of theoptical SW.

FIG. 67 is a diagram illustrating another aspect of the monitoring unit.

FIG. 68 is a diagram illustrating still another aspect of the monitoringunit.

FIG. 69 is a diagram illustrating still another aspect of the monitoringunit.

FIG. 70 is a diagram illustrating a configuration example in a firstmodification example of the subscriber device and the optical GW controlunit.

FIG. 71 is a flowchart illustrating an initial setting process of theoptical access system according to the first modification example of thesubscriber device and the optical GW control unit.

FIG. 72 is a diagram illustrating a configuration example in a secondmodification example of the subscriber device and the optical GW controlunit.

FIG. 73 is a flowchart illustrating an initial setting process of theoptical access system according to the same configuration example.

FIG. 74 is a diagram illustrating a modification example of the opticalaccess system.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the drawings. The same constituents are denotedby the same reference numerals throughout the drawings, and descriptionthereof will not be made. In the following description, first, a basicconfiguration in the present invention will be described, and thenspecific embodiments will be described.

(Basic Configuration)

First, a basic configuration of the present invention will be describedwith reference to FIGS. 1 to 41 .

FIG. 1 is a diagram illustrating a basic configuration example of anoptical communication system 1 of the present embodiment. The opticalcommunication system 1 includes one or a plurality of optical switches(SWs) 10. Although two optical SWs 10 are illustrated in the drawing,the number of optical SWs 10 is freely selected. The optical SWs 10 areconnected to a control unit 20.

In a case where the optical SW 10 is controlled with an optical signal,the optical SW 10 includes at least an optical receiver that receives anoptical signal, but description thereof will be omitted in the followingdescription.

The optical SW 10 communicates with another optical SW 10 via an opticalcommunication network 30. For example, a WDM network including varioustopologies can be used as the optical communication network 30. One ormore subscriber devices 40 are connected to the optical SW 10. Thesubscriber device 40 is connected to the optical SW 10 via, for example,an optical access network such as a PON. The subscriber device 40 has anoptical transceiver 41. The optical transceiver 41 is a configurationexample of an optical transmission unit and an optical reception unit ina subscriber device. The optical transceiver 41 includes an opticaltransmitter (Tx) 42 and an optical receiver (Rx) 43. The opticaltransceiver 41 is a wavelength tunable optical transceiver. As theoptical transceiver 41, for example, a conventional optical transceiverwith an auxiliary management and control channel (AMCC) function may beused.

The control unit 20 (an operation system (OpS) or the like may beincluded therein, or the OpS may include the control unit 20; the sameapplies hereinafter) may be connected to any port of the optical SW 10,for example, a port 2. The control unit 20 may be installed in abuilding different from that of the optical SW 10 and connected to theoptical SW 10 or an optical SW controller (not illustrated in FIG. 1 )via a network. The control unit 20 may be connected to a port that isnot connected to the subscriber device 40, another optical SW 10, ahigher network, a transmission line to another ground, or the like amongthe ports of the optical SW 10. The control unit 20 may be installed foreach optical SW 10 or may be installed for the plurality of optical SWs10.

In a case where the control unit 20 controls the optical SW 10 with anoptical signal, the control unit 20 includes one or a plurality ofoptical transceivers 21. The optical transceiver 21 is a configurationexample of an optical transmission unit and an optical reception unit inthe control unit 20. The optical transceiver 21 includes an opticaltransmitter (Tx) 22 and an optical receiver (Rx) 23. The opticaltransceiver 21 is a variable wavelength optical transceiver. The casewhere there are a plurality of optical transceivers 21 is suitable for acase where a connectable port is different for each port of the opticalSW 10, a case where ports for controlling the optical SW 10 and thesubscriber device 40 are different, a case where a control target is atleast one of the plurality of optical SWs 10 or the subscriber device 40connected to the plurality of optical SWs 10 and connectable ports aredifferent, or the like. A single optical transceiver may be employed byproviding connection using a transmission line in a case where there area plurality of optical SWs 10, and providing return connection using areturn transmission line or the like that will be described later in acase where ports are different. When the control unit includes atransmitter and the subscriber device includes a receiver, atransmission side of the control unit 20 is connected to a receptionside of the subscriber device 40, and when the control unit 20 includesa receiver and the subscriber device 40 includes a transmitter, thereception side of the control unit 20 is connected to the transmissionside of the subscriber device 40.

In a case where only an optical transceiver or a modulation unit of themonitoring unit that will be described later is used, the opticaltransceiver does not have to be provided. In a case where the controlunit 20 controls the subscriber device 40 with an optical signal, whenthe control unit 20 performs a wavelength allocation process or the likeon the subscriber device 40 with an optical signal via the optical SW10, the optical SW 10 is controlled to transmit and receive an opticalsignal between the subscriber device 40 and the control unit 20, andafter the wavelength allocation process, the optical SW 10 is controlledto output the optical signal input from a transmission line to a portcorresponding to a transfer destination specified by a subscriber, thesubscriber device 40, a port of the optical SW 10, a wavelength of theoptical signal, a combination of the subscriber device 40 and thewavelength of the optical signal, a combination of the port and thewavelength of the optical signal, or the like.

In a case where the wavelength allocation process or the like isperformed via the monitoring unit at the preceding stage with respect tothe optical SW 10, the optical SW 10 is controlled to transmit andreceive an optical signal between the monitoring unit and the subscriberdevice 40, and output the optical signal to a port corresponding to aspecified transfer destination after the allocation process.

In a case where the wavelength allocation process or the like isperformed via the monitoring unit at the subsequent stage with respectto the optical SW 10, the optical SW 10 is controlled to output anoptical signal to a port corresponding to a specified transferdestination, the optical signal is transmitted and received between themonitoring unit and the subscriber device 40 in a state in which theoutput from the port is blocked by a blocking unit, and after theallocation process, the blocking is canceled.

In a case where the wavelength allocation process or the like isperformed before connection to the optical SW 10, after the wavelengthallocation process, the optical SW 10 is controlled to output an opticalsignal to a port corresponding to a specified transfer destination.

The control unit 20 has or is connected to a management database (DB)such as a SW connection table and a wavelength table.

In a case where the control unit 20 is connected to the management DB,information regarding a user and a use wavelength is exchanged with themanagement DB. The management DB stores a use wavelength, destinationinformation, and transfer destination information of each user. Forexample, in a case of a ground A or the like, the destination and thetransfer destination are represented by the ground A and a ground B, andin a case of the subscriber device 40 or the like, the destination andthe transfer destination are represented by an identifier of thesubscriber device 40, or an identifier of a transmission line thereof ora port to which the device is connected, an identifier of a devicethrough which a signal passes on the way, a component thereof, or afunction thereof, or an identifier of a port to which the device or thecomponent is connected. The management DB manages information regardinga user connected to the optical access system.

The SW connection table indicates a connection destination of each portof the optical SW 10. That is, a port to and from which an opticalsignal is input and output can be used as information for identifying asubscriber device, a control unit, a monitoring unit, a ground, or thelike that is a transmission source or a transmission destination of theoptical signal.

The wavelength table is data indicating a wavelength allocated to eachsubscriber device 40 or the like. The wavelength table may be dividedinto a user wavelength table and an inter-station wavelength table.

The user wavelength table indicates, for example, a wavelength used foruser transmission, a wavelength used for reception, an availablewavelength not being used for transmission and reception, and awavelength that cannot be used due to a failure.

The inter-station wavelength table indicates, for example, a wavelengththat a certain ground uses for communication with each of other grounds,an available wavelength that is not used for communication with each ofthe other grounds, and a wavelength that cannot be used forcommunication with each of the other grounds due to a failure.

In order to allocate a wavelength corresponding to a transferdestination on a path to a communication destination to the subscriberdevice 40, first, an optical transceiver of the subscriber device 40 orthe like and the optical transceiver of the control unit 20 communicatewith each other. The control unit 20 refers to the wavelength table andselects a wavelength to be allocated to the subscriber device 40 or thelike according to a transfer destination on a path to a communicationdestination.

For example, a wavelength controller of the control unit 20 refers toinformation indicating a wavelength used by a user or a service, andallocates the wavelength to be used by the user. The wavelengthcontroller manages and controls information regarding which user isconnected to which port of the optical SW 10 and which wavelength isused by sharing each piece of connection information.

When a wavelength is selected, in a case where the wavelength ismultiplexed in a section configuring an intermediate path andidentification is performed by using a wavelength, a free wavelength inthe section configuring the path is an available wavelength, and thewavelength is selected from among available wavelengths.

On the other hand, in a case where it is not necessary to consider afree wavelength in a section in which wavelength multiplexing is notperformed in the section configuring an intermediate path, andidentification and branching are not performed by using only awavelength (for example, time division multiplexing, code divisionmultiplexing, mode division multiplexing, core division multiplexing,core wire multiplexing, space division multiplexing, frequency divisionmultiplexing, polarization division multiplexing, or a combinationthereof, or a combination thereof and wavelength division multiplexing),a wavelength that is not a free wavelength in the section may also beselected as an available wavelength if identification and branching arepossible in the section. In a case where wavelength conversion isperformed in the middle of a path, a free wavelength in a sectionconfiguring a path to wavelength conversion or a free wavelength when awavelength is not multiplexed or identification and branching are notperformed by using only a wavelength in a section configuring anintermediate path before wavelength conversion does not have to beselected.

As described above, since the wavelength to be selected does not dependonly on a usage status of the wavelength in the section configuring theintermediate path, it is desirable that the wavelength table indicatesavailable wavelengths in consideration of not only a free wavelength butalso a combination with another multiplexing. Since an availablewavelength depends on a usage status or a multiplexing status of asection configuring an intermediate path, the control unit can use ANDof available wavelengths of sections configuring the path(alternatively, OR of wavelengths that cannot be identified or separatedby factors other than a wavelength).

In a case where destination ports of the optical SW 10 are set by thesubscriber device 40 that transmits an optical signal and a wavelength,and the ports of the optical SW 10 are divided into two groups, forexample, a port 1 and a port 2, and connection is made between thegroups and is not made within the group, available wavelengths may bedifferent in a direction from the port 1 which is one group to the port2 which is the other group and a direction from the port 2 which is theother group to the port 1 which is one group.

In a case where the same control unit controls or manages all thesections configuring the path, the wavelength allocation process isclosed. However, in a case where a plurality of control units or anexternal device controls or manages all the sections, the wavelengthallocation process may be controlled by operating in cooperation, or byreceiving use authority for the wavelength table itself in whichavailable wavelengths are known or values thereof.

The control unit 20 sets the selected wavelength in the subscriberdevice 40 by using a control signal. Thereafter, the control unit 20sets the optical SW 10 to perform outputting according to a destinationor a transfer destination of the optical signal transmitted from thesubscriber device 40.

In a case where the subscriber devices 40 oppose each other via theoptical SW 10, this connects the opposing subscriber devices 40. In acase where a signal passes through a device, a component, or afunctional unit in the middle of the path connected between thesubscriber devices 40, connection is made after the signal passesthrough the device, the component, or the functional unit. The opticalSW 10 may connect the subscriber device 40, the device, the component,or the functional unit through which the signal passes, and the opposingsubscriber device 40 with the same wavelength as light or afterperforming photoelectric conversion or other processes, or may connectthem with different wavelengths in at least some paths as light or afterperforming photoelectric conversion or other processes. For example, ina case where a device, a component, or a functional unit through asignal passes in the middle of the path and both subscriber devices areconnected to the same optical SW, routing is performed from thesubscriber device to the next device, component, or function throughwhich the signal passes, from the device, the component, or the functionthrough which the signal passes to the next device, component, orfunction through which the signal passes, or from the last device,component, or function through which the signal passes to the opposingsubscriber device. Routing from the subscriber device that is acommunication source to the opposing subscriber device that is acommunication partner is a setting in a case where a signal does notpass through a device, a component, or a function through which thesignal is required to pass. In routing, identification of multiplexingprocesses of wavelengths or the like may be applied to parameters, inaddition to a transmission source and a destination or a transferdestination including transmission source and an intermediate path. Thisis suitable in a case where a routing destination aggregates andtransmits a plurality of optical signals having different wavelengths oroptical frequencies in the same station or in an optical SW or the likeat another ground, or a case where a plurality of optical signals havingdifferent wavelengths or optical frequencies is demultiplexed anddistributed to different devices, components, functions, or subscriberdevices.

The control unit 20 allocates a wavelength used for communication by thesubscriber device 40 by using, for example, an AMCC function using acontrol signal that is slower than a main signal that is an opticalsignal between the subscriber devices 40 and can be superimposed on themain signal. Hereinafter, communication between the subscriber device 40and the control unit 20 will be exemplified by the AMCC function, butthe present invention is not limited thereto. In particular, in a casewhere initial setting or setting change of a wavelength or the like isperformed in a state in which the main signal is not received by theopposing device, the control signal may not use another AMCC or the likedifferent from the main signal, and may be exchanged as the main signal.Exchange may be performed according to any modulation method as long asthe modulation method can be realized by functions of the subscriberdevice 40 and the control unit 20.

For example, in order to allocate a wavelength corresponding to atransfer destination on a path to a communication destination to thesubscriber device 40, first, the optical transceiver 41 of thesubscriber device 40 and the optical transceiver 21 of the control unit20 perform communication by using the AMCC. The control unit 20 refersto the wavelength table and selects a wavelength to be allocated to thesubscriber device 40 according to the transfer destination on the pathto the communication destination. As an example, the control unit 20selects a wavelength from among free wavelengths that are not used inother paths in a link for wavelength multiplexing on the path. Thecontrol unit 20 may allocate individual wavelengths to the respectivesubscriber devices 40. The control unit 20 sets the selected wavelengthin the subscriber device 40 by using a control signal using the AMCC.Thereafter, the control unit 20 switches the optical SW 10 to output theoptical signal transmitted from the subscriber device 40 to atransmission line corresponding to the transfer destination on the pathto the communication destination.

The control unit 20 may control the optical switch to perform routingaccording to destination information. As the destination information, astate such as a set including a subscriber device, a wavelength, aninput port, and an output port, or a set including a subscriber device,an input port, or an output port and a wavelength may be used.

The following embodiment will be mainly described in a case where a setincluding a subscriber device and a wavelength is used as destinationinformation.

Consequently, the opposing subscriber devices 40 are connected.

The control unit 20 may perform a wavelength change process ofinstructing the subscriber device 40 to which the wavelength has beenallocated to change the wavelength. For example, the target subscriberdevice 40 is specified on the basis of monitoring information outputfrom a monitoring unit that will be described later, and the wavelengthchange process is performed on the specified subscriber device 40.

The instruction from the control unit 20 to the subscriber device 40 maybe given on a path at the time of initial setting, or may be given bythe monitoring unit or the like.

The control unit 20 controls the optical SW 10 or a blocking unit, ifany, such that the optical signal of the target subscriber device 40 isnot transmitted during the wavelength change. In a case where thecontrol unit 20 directly controls the subscriber device 40 by an opticalsignal, the optical SW 10 is controlled such that the optical signal istransmitted and received between the subscriber device 40 and thewavelength controller.

For example, in a case where there is no other influence on the outputside before the wavelength change, an output port is switched after thewavelength change, and in a case where there is no other influence onthe output side after the wavelength change, the output port is switchedbefore the wavelength change. The transmission may be stopped by adevice other than the optical SW 10.

For example, a transmission line from the optical SW 10 to thesubscriber device 40 or with the subscriber device 40 is removed, andconnection is reestablished after the setting. Alternatively, atransmission line, the optical SW 10, a combining/branching device, amultiplexer/demultiplexer, and a blocking unit at a connection pointthereof are provided, and the blocking unit performs blocking beforewavelength change, and performs setting before or after switching theoutput port as necessary to cancel the blocking.

For example, after the wavelength change process, the optical SWcontroller controls the optical SW 10 to output an optical signal havingthe changed wavelength from the subscriber device 40 from the port 2according to a communication destination or a transfer destination.

At the time of wavelength switching, for example, in a case where thewavelength switching affects another subscriber device 40, the opticaloutput in the path is blocked. Specifically, transmission of the opticalsignal is stopped, the connection to the optical SW 10 is canceled, theconnection from the input side to the output side of the optical SW 10is canceled, and the optical signal is blocked by, for example, ablocking unit included in a monitoring unit of a shutter or the like.

In the wavelength allocation process, the optical SW controller controlsthe path in the optical SW 10 such that the optical SW 10 does nottransmit the optical signal of the subscriber device 40 that is awavelength allocation target. That is, the optical SW controllercontrols the path in the optical SW 10 such that the optical signaltransmitted from the subscriber device 40 is not output to a port(another port) other than the port connected to the monitoring unit ofthe subscriber device 40 that is a wavelength allocation target.

In a case where there is no particular influence even if an outputdestination of the optical SW 10 is switched before the wavelength isset (before the wavelength is allocated), the optical SW controller mayswitch the output destination of the optical SW 10 before the wavelengthis changed. At the time of the wavelength allocation process, afunctional unit other than the optical SW 10 may stop transmission ofthe optical signal transmitted from the subscriber device 40.

In a case where the wavelength switching is associated with switching ofthe optical SW 10 and the wavelength is switched in a state in which theoptical SW 10 is connected to the path before or after the switching,there is no influence.

The wavelength allocation process (wavelength setting) and the pathsetting process are executed in this order. The optical SW controllerswitches an output destination (path) of the optical SW 10 after thewavelength change such that there is no particular influence even if theoutput destination of the optical SW 10 is switched.

For example, in a case where a first port and a first wavelength “λ1”are used before switching, and a second port and a second wavelength“λ2” are used after switching, the following may be used.

(1) In a case where there is no subscriber device 40 using the firstport and the second wavelength “λ2”:

Switching from the first wavelength “λ1” to the second wavelength “λ2”at the first port has no influence. In this case, it is possible toperform wavelength switching before port switching.

(2) In a case where there is the subscriber device 40 using the firstport and the second wavelength “λ2”:

Switching from the first wavelength “λ1” to the second wavelength “λ2”at the first port has influence. In this case, it is not possible toperform wavelength switching before port switching.

(3) In a case where there is no subscriber device 40 using the secondport and the first wavelength “λ1”:

Switching from the first wavelength “λ1” to the second wavelength “λ2”at the second port has no influence. In this case, it is possible toperform wavelength switching before port switching.

(4) In a case where there is the subscriber device 40 using the secondport and the first wavelength “λ1”:

Switching from the first wavelength “λ1” to the second wavelength “λ2”at the second port has influence. In this case, it is not possible toperform wavelength switching before port switching.

In the above “(1)” and “(3) or (4)”, wavelength switching can beperformed before port switching.

In the above “(1) or (2)” and “(3)”, wavelength switching can beperformed before port switching.

In the above “(2)” and “(4)”, wavelength switching cannot be performedbefore port switching, and it is necessary to stop or block an opticalsignal.

In the wavelength allocation process, the wavelength controller executesthe wavelength allocation process on the subscriber device 40 that is awavelength allocation target via the monitoring unit. For example, thewavelength controller executes a process of allocating the samewavelength as or a new wavelength different from a wavelength used whenthe abnormality is detected on the subscriber device 40 that is awavelength allocation target.

In the path setting process, the optical switch controller controls thepath in the optical SW 10 such that the subscriber device 40 that is awavelength allocation target is connected to a port (another port) otherthan the port connected to the monitoring unit of the subscriber device40 that is a wavelength allocation target. For example, the opticalswitch controller controls the optical SW 10 to output an optical signalinput from a transmission line of the subscriber device 40 that is awavelength allocation target to a port (another port) specifiedaccording to a transfer destination. Here, the transfer destination isspecified according to a subscriber, the subscriber device 40, the portof the optical SW 10, a wavelength of the optical signal, a combinationof the subscriber device 40 and the wavelength of the optical signal, acombination of the port 1 and the wavelength of the optical signal, orthe like.

The optical SW 10 is provided in, for example, an optical gateway (GW).An example of the optical SW 10 provided in the optical GW will bedescribed with reference to FIGS. 2 to 15 .

FIG. 2 is a diagram illustrating a configuration example of an opticalSW 10 a. The optical SW 10 a is connected to the plurality oftransmission lines 50, and outputs an optical signal input from any ofthe transmission lines 50 to the other transmission line 50. Thetransmission line 50 is, for example, an optical fiber. The optical SW10 a includes ports 11-1-1 to 11-1-P (where P is an integer of 1 ormore) and ports 11-2-1 to 11-2-Q (where Q is an integer of 1 or more,and at least one of P and Q is 2 or more). In a case where any of theports 11-1-1 to 11-1-P is not specified, the ports will be collectivelyreferred to as a port 11-1, and in a case where any of the ports 11-2-1to 11-2-Q is not specified, the ports will be collectively referred toas a port 11-2. A transmission line 50 connected to the port 11-1 willbe referred to as a transmission line 50-1, and the transmission line 50connected to the port 11-2 will be referred to as a transmission line50-2.

Each port 11-1 is connected to the subscriber device 40 via thetransmission line 50-1. Each port 11-2 is connected to the subscriberdevice 40 via the transmission line 50-2. The subscriber device 40 is,for example, an ONU. The transmission line 50-2 may be connected to anoptical communication network 30 that is a higher network. In this case,a direction of the subscriber device 40 connected via the transmissionline 50-1 is a downlink direction, and a direction of the higher networkconnected via the transmission line 50-2 is an uplink direction. Thetransmission line 50-2 may include an optical communication device suchas another optical SW 10.

The ports 11-1-1, 11-1-2, 11-1-3, . . . are respectively connected tothe subscriber devices 40 a-1, 40 a-2, 40 a-3, . . . that are thesubscriber devices 40 at the ground A via transmission lines 50-1. Anyone of the ports 11-2 (in the same figure, the port 11-2-1) is connectedto a wavelength controller 25 that will be described later. Some ports11-2-i, 11-2-(i+1), 11-2-(i+2), . . . are respectively connected to thesubscriber devices 40 b-1, 40 b-2, 40 b-3, . . . that are the subscriberdevices 40 at the ground B via the transmission line 50-2 (where i is aninteger of 2 or more). Some ports 11-2-j, 11-2-(j+1), 11-2-(j+2), . . .different from the ports 11-2 connected to the subscriber devices 40 atthe ground B are respectively connected to the subscriber devices 40c-1, 40 c-2, 40 c-3, . . . that are the subscriber devices 40 at theground C via the transmission line 50-2 (where j is an integer of 2 ormore). The optical SW 10 a outputs an optical signal input from the port11-1 to the port 11-2, and outputs an optical signal input from the port11-2 to the port 11-1. Here, an optical communication device such asanother optical SW or the optical communication network 30 may beinterposed between the subscriber device 40 at the ground A, and thesubscriber device 40 at the ground B and the subscriber device 40 at theground C.

The optical SW 10 a is connected to the control unit 20. The controlunit 20 includes the wavelength controller 25 and the optical SWcontroller 26. The wavelength controller 25 performs a wavelengthallocation process of receiving a wavelength allocation request from thesubscriber device 40 by using an optical signal, allocating a wavelengthcorresponding to a transfer destination on a path to a communicationdestination to the subscriber device 40 that has transmitted therequest, and notifying the subscriber device 40 of the allocatedwavelength by using an optical signal. For example, the wavelengthcontroller 25 may dynamically allocate a wavelength corresponding to atransfer destination on a path to a communication destination to thesubscriber device 40 that has transmitted the request. For opticalsignals transmitted and received between the wavelength controller 25and the subscriber device 40, it is desirable to use a control signalsuperposition method that does not depend on a communication protocol ofan optical signal (main signal) between the subscriber devices 40. Foroptical signals transmitted and received between the wavelengthcontroller 25 and the subscriber device 40, for example, a protocol-freeAMCC is used. A main signal may be transmitted and received and setwithout using a control signal superimposed by the AMCC or the like.

While the wavelength allocation process is being executed, the opticalSW controller 26 controls the optical SW 10 a such that optical signalsare transmitted and received between the subscriber device 40 and thewavelength controller 25. After the wavelength allocation process, theoptical SW controller 26 controls the optical SW 10 a to output theoptical signal input from the transmission line 50 to the transmissionline 50-2 corresponding to a transfer destination on a path to acommunication destination specified by a combination of the subscriberdevice 40 that has transmitted the input optical signal and a wavelengthof the input optical signal.

Each transmission line 50-2 includes a monitoring unit 60. In the samefigure, only one monitoring unit 60 is illustrated. The monitoring unit60 includes a power splitter 61. The power splitter 61 branches anoptical signal transmitted through the transmission line 50-2. Themonitoring unit 60 monitors the optical signal branched by the powersplitter 61. The monitoring unit 60 generates monitoring informationbased on a monitoring result and outputs the generated monitoringinformation. The monitoring information is information indicating amonitoring result or information obtained from the monitoring result.For example, when an abnormality or the like of a communication statusbetween the subscriber devices 40 is detected according to a changerequest from the subscriber device 40 using a control signal or bymonitoring an optical signal, monitoring information in which the factthat the abnormality in the communication status has occurred andinformation for specifying the subscriber device 40 in which theabnormality in the communication status has occurred are set is output.Examples of the abnormality in the communication status include awavelength shift, an increase or decrease in output, and a communicationabnormality (error). An example of an output destination of themonitoring information is the control unit 20. In a case where theabnormality is detected, the control unit 20 controls the optical SW 10,the monitoring unit, or the blocking unit such that the optical signalof the target subscriber device 40 is not transmitted. In a case wherethe control unit 20 directly controls the subscriber device 40 with anoptical signal, the optical SW 10 is controlled to connect thesubscriber device 40 to the control unit 20 again. The control unit 20performs a process of allocating the same wavelength as or a newwavelength different from the wavelength at the time of detection of theabnormality, similarly to when the new subscriber device 40 isconnected. Consequently, the optical SW 10 inputs an optical signalhaving the wavelength before or after the change from the subscriberdevice 40 to a port of the subscriber device 40 before the change. In acase where the connection in the optical SW is not recovered from theabnormal state even when a predetermined process such as restart orreallocation is performed a predetermined number of times due to afailure, a Rogue ONU, or the like, or from an identification number or abehavior of a subscriber device registered in a blacklist or performinga similar operation in the past, the connection in the optical SW may bereleased, the connection may be blocked by a blocking unit, or setting,connection, or transfer may be stopped. During communication withanother subscriber device 40, the power splitter 61 may branch a controlsignal transmitted by the subscriber device 40 or superimpose and outputthe control signal to the subscriber device 40 or the like.

In a case where the subscriber device 40 is connected to thetransmission line 50-2, the control unit 20 may be connected to the port11-1. Alternatively, in a case where the subscriber device 40 isconnected to the transmission line 50-2, the subscriber device 40connected to the transmission line 50-2 may be connected to the controlunit 20 via a return transmission line 73. The return transmission line73 is an optical fiber, an optical switch, an opticalcombining/branching device, or an optical multiplexer/demultiplexer thatinputs an optical signal output from the port 11-1-p 1 to another port11-1-p 2 (where p1 and p2 are integers of 1 or more and P or less). Inthis case, the optical signal transmitted from the subscriber device 40b or 40 c is input to the optical SW 10 a via the transmission line50-2. The optical SW 10 a outputs the optical signal input from thetransmission line 50-2 to the port 11-1-p 1, and receives the opticalsignal transmitted through the return transmission line 73 from the port11-1-p 2. The optical SW 10 a outputs the optical signal input from theport 11-1-p 2 to the control unit 20 from the port 11-2-1. As a result,the subscriber device 40 b or 40 c and the control unit 20 areconnected.

The wavelength controller 25 may perform a wavelength change process ofinstructing the subscriber device 40 subjected to the wavelengthallocation process to change the wavelength or the like. Here, thewavelength change process will be described by an example in which thesubscriber device 40 communicates with the control unit with themonitoring information as a trigger. For example, the wavelengthcontroller 25 specifies the subscriber device 40 that is a wavelengthchange target on the basis of the monitoring information output from themonitoring unit 60, and performs a wavelength change process on thespecified subscriber device 40. The optical SW controller 26 controlsthe optical SW 10 a such that an optical signal is transmitted andreceived between the subscriber device 40 and the wavelength controller25 during the wavelength change process. After the wavelength changeprocess, the optical SW controller 26 controls the optical SW 10 a tooutput the optical signal transmitted from the subscriber device 40 atthe changed wavelength to the transmission line 50-2 corresponding tothe transfer destination on the path to the communication destination.For example, after the wavelength change process, the optical SWcontroller 26 controls the optical SW 10 a to output the optical signalhaving the changed wavelength from the subscriber device 40 to thetransmission line 50-2 corresponding to the transfer destination on thepath to the communication destination used for a combination of thesubscriber device 40 that is a transmission source and the wavelengthbefore the change. Alternatively, the optical SW 10 a may be controlledto output the optical signal having the changed wavelength to thetransmission line 50-2 different from that before the wavelength change.In this case, before and after the wavelength change process, thesubscriber devices 40 that are transfer destinations on the path to thecommunication destination are different. The wavelength controller 25may receive a wavelength change request from the subscriber device 40during communication or after the end of communication, and perform awavelength change process on the subscriber device 40 that is a requestsource. Both the wavelength used for transmission and the wavelengthused for reception by the subscriber device 40 may be changed by thewavelength change process, or either thereof may be changed.

The monitoring information used in the wavelength changing process maybe, for example, a change request from the subscriber device 40 using acontrol signal, an abnormality in a communication status such as awavelength deviation, an increase or decrease in output, or acommunication abnormality (error), a deviation from designation,setting, or an allowable range of a wavelength, a modulation method, aprotocol, or the like to be used, use of an unallocated wavelength, orabnormality detection such as signal interruption. The monitoringinformation may be a trigger other than a monitoring signal, forexample, a change request for a transmission destination or the like viaa main signal or via a signal not passing through an optical SW, or maybe a request for abnormality detection, stoppage, or change from adevice inside or outside a network, such as a transmission line or amanagement system. In a case where abnormality detection, stop, orchange is requested and the wavelength or the like is not changed to adesignated, set, or allowable range, the subscriber device 40 may beinterrupted by a shutter or the like in a state in which an instructionor a signal for restart or the like is connected to the control unit ora signal is not output to the transmission line. The exchange betweenthe control unit 20 and the subscriber device 40 may be performed byusing an AMCC or may be performed by using a main signal. In a casewhere the subscriber device 40 is not compatible with an AMCC, it ispreferable to use the main signal. In a case where a wavelength or thelike before the switching does not adversely affect an opposing devicebefore the switching, a path with the opposing subscriber device 40 maybe set by the monitoring unit or the like while being connected withoutbeing switched to the control unit 20. In a case where the wavelength orthe like after the switching does not adversely affect the opposingdevice after the switching, the path with the opposing subscriber device40 may be set by the monitoring unit or the like after being switchedwithout being switched to the control unit 20.

FIG. 3 is a diagram illustrating a configuration example of an opticalSW 10 b having a return circuit for return communication. In the samefigure, the same portions as those of the optical SW 10 a illustrated inFIG. 2 are denoted by the same reference numerals, and the descriptionthereof will be omitted. In FIG. 3 , the control unit 20 is notillustrated. In the following description as well, description of thecontrol unit 20 will be omitted in the drawings when it is notparticularly necessary. The optical SW 10 b is connected to a returntransmission line 51. The return transmission line 51 is an opticalfiber, an optical switch, an optical combining/branching device, or anoptical multiplexer/demultiplexer that inputs an optical signal outputfrom the port 11-2 to another port 11-2. Consequently, the optical SW 10b enables return communication.

In a case where a port that is an output destination of the opticalsignal is set by a combination of the subscriber device 40 that is atransmission source and the wavelength, a destination may be differentbetween a direction from the port 11-1 to the port 11-2 to which thereturn transmission line 51 is connected and a direction from the port11-2 to which the return transmission line 51 is connected to the port11-1.

FIG. 4 is a diagram illustrating a configuration example of the opticalSW 10 c that performs uplink multicast using a one to one returntransmission line and a one to other return transmission line opposingeach other. In the same figure, the same portions as those of theoptical SW 10 a illustrated in FIG. 2 are denoted by the same referencenumerals, and the description thereof will be omitted. The optical SW 10c includes a distribution unit 58 that distributes an optical signaloutput from the port 11-2 into a plurality of signals and inputs theplurality of distributed optical signals to different ports 11-1. InFIG. 4 , the optical SW 10 c inputs the optical signal output from theport 11-2 to the other port 11-2 via the return transmission line. Theoptical SW 10 c outputs the input optical signal to the port 11-1 towhich a 1×N power splitter 71 is connected. The optical signal outputfrom the port 11-1 is distributed by the power splitter 71 and input toa plurality of other ports 11-1. The optical SW 10 c outputs the opticalsignals input from the plurality of ports 11-1 to different ports 11-2,respectively. Bidirectional communication may also be performed. Theoptical signal in the downlink direction is routed in a reversedirection to the uplink direction.

The optical SW 10 c may receive an optical signal having a plurality ofwavelengths from the port 11-1. In this case, the optical SW 10 cdistributes the optical signal having a plurality of wavelengths inputfrom the port 11-1 by using the distribution unit 58, and outputs thedistributed optical signals to the respective subscriber devices 40connected to the ports 11-2 or transmission lines connected to othergrounds. The subscriber device 40 connected to the port 11-2 selects andreceives an optical signal having a predetermined wavelength amongoptical signals having a plurality of wavelengths. The transmissionlines connected to the other grounds may transmit optical signals havinga plurality of wavelengths without any change or may transmit opticalsignals having wavelengths selected by a WDM device illustrated in FIG.6 that will be described later.

FIG. 5 is a diagram illustrating a configuration example of the opticalSW 10 d that performs downlink multicast. In the same figure, the sameportions as those of the optical SW 10 a illustrated in FIG. 2 aredenoted by the same reference numerals, and the description thereof willbe omitted. The optical SW 10 d includes a distribution unit 59 thatdistributes an optical signal output from the port 11-1 into a pluralityof signals and inputs the plurality of distributed optical signals todifferent ports 11-2, respectively. In FIG. 5 , the optical SW 10 dinputs the optical signal output from the port 11-1 to another port 11-1via a return transmission line. The optical SW 10 d outputs the inputoptical signal to the port 11-2 to which a 1×N power splitter 72 isconnected. The optical signal output from the port 11-2 is distributedby the power splitter 72 and input to the plurality of different ports11-2. The optical SW 10 d outputs the optical signals input from theplurality of ports 11-2 to different ports 11-1, respectively.

An optical signal having a plurality of wavelengths may be input to theoptical SW 10 d from the port 11-2. In this case, in the optical SW 10d, the optical signal having a plurality of wavelengths input from theport 11-2 is distributed by the distribution unit 59, and thedistributed optical signals are output to the respective subscriberdevices 40 connected to the ports 11-1. Each of the subscriber devices40 connected to the ports 11-1 selects and receives an optical signalhaving a predetermined wavelength from among the received opticalsignals having a plurality of wavelengths.

FIG. 6 is a diagram illustrating a configuration example of an opticalSW 10 e that performs WDM transmission. In the same figure, the sameportions as those of the optical SW 10 a illustrated in FIG. 2 aredenoted by the same reference numerals, and the description thereof willbe omitted. The optical SW 10 e is connected to one or more WDM devices80. The WDM device 80 is an example of a multiplexer/demultiplexer. TheWDM device 80 multiplexes optical signals having different wavelengthsoutput from the plurality of ports 11-2 and outputs a multiplexedoptical signal to a multiplex communication transmission line 90. TheWDM device 80 demultiplexes an optical signal received via the multiplexcommunication transmission line 90 according to wavelengths, and inputsthe demultiplexed optical signals to the plurality of ports 11-2. Asdescribed above, the WDM device 80 has functions of a multiplexingdevice and a demultiplexing device. As a function of the multiplexingdevice, optical signals having different wavelengths output from theplurality of ports 11-2 of the optical SW 10 e are multiplexed andoutput to the multiplex communication transmission line 90. As afunction of the demultiplexing device, an optical signal received viathe multiplex communication transmission line 90 is demultiplexedaccording to wavelengths, and the demultiplexed optical signals arerespectively input to a plurality of different ports 11-2 of the opticalSW 10 e. The optical SW 10 e that performs WDM transmission may connectthe return transmission line 51 illustrated in FIG. 3 to the port 11-2that is not connected to the WDM device 80.

The multiplex communication transmission line 90 includes a monitoringunit 65. The monitoring unit 65 includes a power splitter 66 and WDMdevices 67 and 68. The power splitter 66 branches an optical signaltransmitted through the multiplex communication transmission line 90.The WDM device 67 demultiplexes an uplink optical signal branched by thepower splitter 66. The WDM device 68 demultiplexes a downlink opticalsignal branched by the power splitter 66. The monitoring unit 65monitors optical signals demultiplexed by the WDM device 67 and the WDMdevice 68. The monitoring unit 65 generates monitoring information basedon a monitoring result and outputs the generated monitoring information.

The monitoring unit 65 may include a power splitter 69 in each of thetransmission lines between the ports 11-2 and the WDM device 80. Thepower splitter 69 branches an optical signal transmitted through thetransmission line between the port 11-2 and the WDM device 80, andoutputs the branched optical signal to the control unit 20.

The wavelength controller 25 may perform a wavelength change process ofinstructing the subscriber device 40 subjected to the wavelengthallocation process to change a wavelength. For example, the wavelengthcontroller 25 specifies the subscriber device 40 that is a wavelengthchange target on the basis of the monitoring information output from themonitoring unit 65, and performs a wavelength change process on thespecified subscriber device 40. The optical SW controller 26 controls,for example, reconnects the optical SW 10 e via the monitoring unit suchthat optical signals are transmitted and received between the subscriberdevice 40 and the wavelength controller 25 during the wavelength changeprocess. In a case where an optical signal having the changed wavelengthis input from the subscriber device 40 after the wavelength changeprocess, the optical SW controller 26 controls the optical SW 10 e tooutput the input optical signal from the port 11-2 corresponding to thetransfer destination on the path to the communication destination. Thewavelength controller 25 may receive a wavelength change request fromthe subscriber device 40 during communication or after the end ofcommunication, and perform a wavelength change process on the subscriberdevice 40 that is a request source.

An example of wavelength change in the optical SW 10 e will be describedwith reference to FIGS. 7 and 8 . FIG. 7 is a diagram illustrating anexample of routing before wavelength change in the optical SW 10 e. Theoptical SW 10 e is connected to the subscriber devices 40 a-1, 40 a-2,40 a-3 . . . that are subscriber devices 40 at the ground A. The WDMdevice 80 connected to the ground B will be referred to as a WDM device80 b, and the WDM device 80 connected to the ground C will be referredto as a WDM device 80 c. The WDM device 80 b transmits and receivesoptical signals having wavelengths λ₁ to λ₁₀ to and from the optical SW10 e, and the WDM device 80 c transmits and receives optical signalshaving wavelengths λ₁₁ to λ₂₀ to and from the optical SW 10 e.

In FIG. 7 , before the wavelength change, the optical SW 10 e outputsthe optical signal having the wavelength λ₁ input from the subscriberdevice 40 a-1 and the optical signal having the wavelength λ₂ input fromthe subscriber device 40 a-2 to the WDM device 80 b from different ports11-2. The subscriber device 40 a-2 transmits a wavelength change requestto the wavelength controller 25 by using a control signal duringcommunication or after the end of communication. Upon receiving thewavelength change request from the subscriber device 40 a-2, thewavelength controller 25 performs a wavelength change process ofinstructing the subscriber device 40 a-2 to change to the wavelengthλ₁₀. The optical SW controller 26, the monitoring unit, or the blockingunit does not output the optical signal having the wavelength λ₁₀received from the subscriber device 40 a-2 until the wavelength changeis completed as necessary, and the optical SW controller 26 controls theoptical SW 10 e to output the optical signal from the port 11-2corresponding to the wavelength λ₁₀ to the WDM device 80 b after theswitching is completed. The wavelength controller 25 may further changethe wavelength used for reception by the subscriber device 40 a-2.

After the wavelength change process, the optical SW controller 26 maycontrol the optical SW 10 e to output the optical signal having thechanged wavelength transmitted from the subscriber device 40 that is atransmission source to the WDM device 80 different from that before thewavelength change. FIG. 8 is a diagram illustrating an example ofrouting after wavelength change in the optical SW 10 e in a case wherethe WDM device 80 that is an output destination is changed. Before thewavelength change, as illustrated in FIG. 7 , the subscriber device 40a-1 performs communication using the wavelength λ₁, and the subscriberdevice 40 a-2-performs communication using the wavelength λ₂ or thewavelength λ₁₀. The subscriber device 40 a-2 transmits a wavelengthchange request to the wavelength controller 25 by using a control signalduring communication or after the end of communication. Upon receiving awavelength change request from the subscriber device 40 a-2, thewavelength controller 25 performs a wavelength change process ofinstructing the subscriber device 40 a-2 to change a wavelength to thewavelength λ₁₁ in order to communicate with the subscriber device 40 atthe ground C. The optical SW controller 26, the monitoring unit, or theblocking unit does not output the optical signal having the wavelengthλ₁₀ input from the subscriber device 40 a-2 until the wavelength changeis completed as necessary, and after the switching is completed, theoptical SW controller 26 controls the optical SW 10 e to output theoptical signal having the wavelength λ₁₁ received from the subscriberdevice 40 a-2 to the WDM device 80 c from the port 11-2 corresponding tothe wavelength λ₁₁. The wavelength controller 25 may further change thewavelength used for reception by the subscriber device 40 a-2.

In a case where the subscriber device 40 a-2 does not change thewavelength used for reception, the wavelength controller 25 may operateas follows. In a case where the wavelength is not used as at least apart of the destination information, the following may not be applied.

(1) The wavelength controller 25 releases the transmission wavelengthused by the subscriber device 40 at the ground B that is a communicationdestination before the wavelength switching. Due to the release of thetransmission wavelength, the path from the subscriber device 40 a-2 tothe subscriber device 40 at the ground B is reset. Thereafter, thewavelength controller 25 reallocates the wavelength that has become afree wavelength due to the release for reception of a signal addressedto the subscriber device 40 a-2 from the subscriber device 40 at theground C that is a new communication destination. This is performed in acase where a wavelength to be used for each subscriber device 40 isunique, and no wavelength other than the free wavelength is allocated.

(2) In a case where the subscriber device 40 connected via the differentmultiplex communication transmission line 90 before and after thewavelength change of the subscriber device 40 a-2 is a communicationdestination, the wavelength used before the wavelength change can bereused without any change. However, although the wavelength is used asthe destination information, for example, in a case where a signalpasses through a different transmission line or in a case where theinput port or the output port of the optical switch is different, pathsare handled to be different even for the same wavelength. In order toenable reuse as described above, in this case, for example, an “inputtransmission line”, an “output transmission line”, or a “combination ofall transmission lines configuring a path” is added to an argumentserving as a condition for determining an output destination of anoptical signal. For example, the output destination is determined by acombination of a transmission line or a port that has received theoptical signal and a wavelength of the optical signal, or a combinationof a transmission line or a port that has received the optical signal,the subscriber device 40 that has transmitted the optical signal, and awavelength of the optical signal.

Although the wavelength change process performed by the subscriberdevice 40 requesting wavelength change has been described above, thesame applies to a wavelength change process performed on the basis ofthe monitoring information.

An optical SW that performs WDM transmission and multicast will bedescribed with reference to FIGS. 9 to 11 . FIG. 9 is a diagramillustrating a configuration example of an optical SW 10 f that performsWDM transmission and uplink multicast. In FIG. 9 , the optical SW 10 fperforms uplink multicast with a single wavelength. As illustrated inFIG. 9 , the optical SW 10 f includes a distribution unit 58 similar tothat in FIG. 4 . In FIG. 9 , multicast is performed on the ground B andthe ground C. The optical SW 10 f outputs an optical signal input fromthe port 11-1 connected to the subscriber device 40 from the port 11-2connected to the return transmission line, and receives the opticalsignal transmitted through the return transmission line from anotherport 11-2. The optical SW 10 f outputs the received optical signal fromthe port 11-1 to which the 1×N power splitter 71 is connected. Theoptical SW 10 f receives the optical signals distributed by the 1×Npower splitter 71 from the plurality of ports 11-1, and outputs one ofthe received optical signals to the port 11-2 connected to the ground Band another optical signal to the port 11-2 connected to the ground C.

The subscriber device 40 may output a WDM signal. For example, thesubscriber device 40 outputs a WDM signal in which the optical signalhaving the wavelength λ₁ and the optical signal having the wavelength λ₂are multiplexed. A plurality of transmission lines between the WDMdevice 80 b and the optical SW 10 f transmit and receive optical signalshaving wavelengths λ₁, λ₂, . . . in order from the top. Similarly, in aplurality of transmission lines between the WDM device 80 c and theoptical SW 10 f, optical signals having wavelengths λ₁, λ₂, . . . aretransmitted and received in order from the top.

In the optical SW 10 f, the WDM signal having the wavelength λ₁ and thewavelength λ₂ input from the ports 11-1 connected to the subscriberdevice 40 is distributed by the distribution unit 58. The optical SW 10f outputs the distributed WDM signal to the port 11-2 corresponding tothe wavelength λ₁ among the ports 11-2 connected to the WDM device 80 b.The optical SW 10 f outputs another distributed WDM signal to the port11-2 corresponding to the wavelength λ₂ among the ports 11-2 connectedto the WDM device 80 c. The WDM device 80 b filters the WDM signal inputfrom the port corresponding to the wavelength λ1 to block the wavelengthλ₂, passes the optical signal having the wavelength λ₁, and outputs theoptical signal to the multiplex communication transmission line 90. TheWDM device 80 c filters the WDM signal input from the port correspondingto the wavelength 22 to block the wavelength λ₁, causes the opticalsignal having the wavelength λ₂ to pass therethrough, and outputs theoptical signal to the multiplex communication transmission line 90.

FIG. 10 is a diagram illustrating a case where the optical SW 10 fperforms uplink multicast to a plurality of grounds by using a pluralityof wavelengths. By providing one or more 1×M power splitters 55 in thetransmission line 50-1, a plurality of subscriber devices 40 can beconnected to the transmission line 50-1 connected to one port 11-1. InFIG. 10 , as a plurality of subscriber devices 40 a-1, the subscriberdevices 40 a-1-1, 40 a-1-2, . . . are connected to one transmission line50-1. The subscriber devices 40 a-1-1, 40 a-1-2, . . . use differentwavelengths. Here, the subscriber device 40 a-1-1 transmits an opticalsignal having the wavelength λ₁, and the subscriber device 40 a-1-2transmits an optical signal having the wavelength λ₂. The optical SW 10f receives, from the port 11-1, an optical signal obtained bymultiplexing the optical signal having the wavelength λ₁ transmitted bythe subscriber device 40 a-1-1 and the optical signal having thewavelength λ₂ transmitted by the subscriber device 40 a-1-2. The opticalSW 10 f outputs the received optical signal from the port 11-2 to whichthe return transmission line is connected, and receives the opticalsignal transmitted through the return transmission line from anotherport 11-2. The optical SW 10 f outputs the received optical signal fromthe port 11-1 to which the 1×N power splitter 71 is connected. Theoptical signals distributed by the 1×N power splitter 71 are input tothe optical SW 10 f from the plurality of ports 11-1.

The optical SW 10 f outputs the optical signals distributed by the powersplitter 71 to the port 11-2 corresponding to the wavelength λ₁ and theport 11-2 corresponding to the wavelength λ₂ among the ports 11-2connected to the WDM device 80 b. The optical SW 10 f outputs theoptical signals distributed by the power splitter 71 to the port 11-2corresponding to the wavelength λ₁ and the port 11-2 corresponding tothe wavelength λ₂ among the ports 11-2 connected to the WDM device 80 c.The WDM device 80 b filters the optical signal input from the portcorresponding to the wavelength λ₁, causes the optical signal having thewavelength λ₁ to pass therethrough, and outputs the optical signal tothe multiplex communication transmission line 90, and filters theoptical signal input from the port corresponding to the wavelength λ₂,causes the optical signal having the wavelength λ₂ to pass therethrough,and outputs the optical signal to the multiplex communicationtransmission line 90. Similarly, the WDM device 80 c filters the opticalsignal input from the port corresponding to the wavelength 1, causes theoptical signal having the wavelength λ₁ to pass therethrough, andoutputs the optical signal to the multiplex communication transmissionline 90, and filters the optical signal input from the portcorresponding to the wavelength λ₂, causes the optical signal having thewavelength λ₂ to pass therethrough, and outputs the optical signal tothe multiplex communication transmission line 90.

FIG. 11 is a diagram illustrating a configuration example of an opticalSW 10 g that performs WDM transmission and downlink multicast. Theoptical SW 10 g has a distribution unit 59 similar to that in FIG. 5 .The optical SW 10 f illustrated in FIGS. 9 and 10 and the optical SW 10g illustrated in FIG. 11 may have a monitoring unit 65 similar to thatin FIG. 6 . The wavelength controller 25 may perform a wavelength changeprocess in the same manner as described above on the subscriber device40 in which the monitoring unit 65 has detected the abnormality in acommunication status.

FIG. 12 is a diagram illustrating a case where the optical SW 10 gperforms WDM transmission and downlink multicast. The connectionconfiguration illustrated in FIG. 12 is different from the connectionconfiguration illustrated in FIG. 11 in that the WDM device 80 connectedto the plurality of ports 11-2 of the optical SW 10 g is replaced with aWDM device 81 connected to the plurality of ports 11-1 and disposed. Oneor more subscriber devices 40 are connected to the WDM device 81 on theside opposite to the port 11-1. The optical SW 10 g receives an opticalsignal having a plurality of wavelengths from another ground from theport 11-2 and outputs the optical signal to the port 11-1 to which thereturn transmission line of the distribution unit 59 is connected. Theoptical signal having the plurality of wavelengths is branched by thepower splitter 72 without any change. The optical SW 10 d receives thebranched optical signals having the plurality of wavelengths from theplurality of ports 11-2, and outputs the received optical signals to anyone of the ports 11-1 connected to the WDM device 81. The WDM device 81filters an optical signal having a wavelength corresponding to the port11-1 to which the optical signal is input from the input optical signalshaving the plurality of wavelengths, causes the optical signal to passtherethrough, and outputs the optical signal having passed to thetransmission line connected to the subscriber device 40.

FIG. 13 is a diagram illustrating a configuration example of an opticalSW 10 h that performs electrical processing on an optical signal. InFIG. 13 , the same constituents as those of the optical SW 10 billustrated in FIG. 3 are denoted by the same reference numerals, anddescription thereof will be omitted. The optical SW 10 h is differentfrom the optical SWs 10 a to 10 g described above in that a port 12-1and a port 12-2 are further provided. The port 12-1 and the port 12-2are connected to an electrical processing unit 84 via transmission lines52. The port 11-1 and the port 11-2 may be used as ports connected tothe electrical processing unit 84 via the transmission lines 52.

Under the control of the optical SW controller 26, the optical SW 10 houtputs the optical signal input from the subscriber device 40 from theport 11-2 or the port 12-1 according to a combination of the subscriberdevice 40 that is a transmission source of the optical signal or theport 11-1 to which the optical signal is input and the wavelength. Underthe control of the optical SW controller 26, the optical SW 10 h outputsthe output destination of the optical signal input from the port 11-2from the port 11-1 or the port 12-1 according to a combination of theport 11-2 to which the optical signal is input and the wavelength.

The optical SW 10 h outputs the optical signal from the port 12-1, andthus drops the optical signal on the electrical processing unit 84. Theelectrical processing unit 84 electrically terminates the droppedoptical signal, performs various types of electrical processing such aserror correction and line concentration, converts the signal into anoptical signal, and inputs the optical signal to the port 12-2 of theoptical SW 10 h. The optical SW 10 h outputs the optical signal inputfrom the electrical processing unit 84 from the port 11-1 or the port11-2 according to a transfer destination on a path to a communicationdestination specified by the combination of the port 12-2 and thewavelength. As described above, the electrical processing unit 84performs O-E (electrical processing addition)-O conversion (O representsoptical, and E represents electrical). The electrical processing unit 84may simply perform O-E-O conversion without performing electricalprocessing for adding a function. The electrical processing unit 84 canalso reduce optical waveform deterioration associated with transmissionby performing 3R reproduction (re-amplification: amplification,re-timing: timing reproduction, and re-shaping: waveform shaping) orperforming 0/1 inversion to use a threshold effect in O-E-O conversionor the like.

A wavelength of an optical signal before being converted into anelectrical signal and a wavelength of an optical signal after beingconverted from an electrical signal may be the same or different. Theelectrical processing unit 84 may multiplex optical signals transmittedfrom the plurality of subscriber devices 40 at an electrical stage,convert the multiplexed signal into a plurality of optical signals, andbranch the plurality of optical signals into separate ports,multiplexers/demultiplexers, or power splitters. The branched opticalsignal may be further branched and output to themultiplexer/demultiplexer at a plurality of wavelengths, or may befurther branched and multicasted by a power splitter. The electricalprocessing unit 84 may perform only multiplexing or only multicast atthe electrical stage. The processing at the electrical stage is suitablefor a case where signals of transceivers of the subscriber device 40having a band smaller than that of the transmission line are bundled andhandled, for example.

Specifically, the optical SW 10 h is connected to the electricalprocessing unit 84 that converts optical signals transmitted from theplurality of respective subscriber devices 40 into electrical signals,multiplexes the electrical signals, processes the multiplexed electricalsignal, converts the electrical signal into an optical signal having aplurality of wavelengths, and inputs the optical signal to the opticalswitch 10 h. The optical switch controller 26 controls the opticalswitch 10 h to output a plurality of optical signals input from thetransmission lines 50-1 to the electrical processing unit 84 accordingto a combination of the plurality of subscriber devices 40 that havetransmitted the plurality of input optical signals and wavelengths ofthe input optical signals, and to output a signal input from theelectrical processing unit 84 to the transmission line 50-2corresponding to a transfer destination on a path to a communicationdestination specified by the wavelength.

In a case where a port to be an output destination of the optical SW isdefined by a combination of a subscriber device that transmits anoptical signal and a wavelength, a destination may be different betweena direction from the port 11-1 to the port 11-2 and a direction from theport 11-2 to the port 11-1 in order to cause the optical signal to passthrough the electrical processing unit 84.

The electrical processing unit 84 includes an optical/electrical (O/E)conversion unit 85, a processing execution unit 86, anelectrical/optical (E/O) conversion unit 87, and a storage unit 88. TheO/E conversion unit 85 converts an optical signal input from the opticalSW 10 h into an electrical signal. The processing execution unit 86includes a processor 861 and an accelerator 862. The processor 861 is,for example, a general-purpose processor such as a central processingunit (CPU). The accelerator 862 is a processor such as a graphicsprocessing unit (GPU). The processor 861 and the accelerator 862 read aprogram from the storage unit 88 and execute the program, and thusperform electrical signal processing on the electrical signal convertedby the O/E conversion unit 85. The processing execution unit 86 mayperform electrical signal processing corresponding to a plurality offunctions. Examples of the electrical signal processing are digitalsignal processing (DSP) for long distance/high speed access, mobilefronthaul processing, and error correction. The E/O conversion unit 87converts the electrical signal into an optical signal having awavelength designated by the optical SW controller 26, and outputs theoptical signal to the optical SW 10 h. The storage unit 88 stores aprogram for the processor 861 and the accelerator 862 to execute afunction of electrical signal processing.

Since the processing execution unit 86 has a device architecture basedon a general-purpose processor, it is possible to add and changeelectrical signal processing and to replace various functions other thanthe transmission function. Since the processing execution unit 86performs DSP for long distance/high speed access, a dedicated largescale integration (LSI) for long distance/high speed access is notrequired, and flexible function deployment according to needs can berealized.

The optical SW 10 h may be connected to a plurality of electricalprocessing units 84. In this case, the optical SW 10 h has ports 12-1and 12-2 connected to the respective electrical processing units 84.Each of the electrical processing units 84 may perform differentelectrical signal processing, or some or all of the electricalprocessing units may perform the same electrical processing.

The processing execution unit 86 and the storage unit 88 may be realizedby using hardware such as an application specific integrated circuit(ASIC), a programmable logic device (PLD), or a field programmable gatearray (FPGA).

FIG. 14 is a diagram illustrating an example of connection using theoptical SW 10 h. The subscriber devices 40-1, 40-2, and 40-3 connectedto the optical SW 10 h are, for example, ONUs. A user 46-1 who uses thesubscriber device 40-1 is a user who performs long-distance orhigh-speed communication. One or more communication devices of the user46-1 are connected to the subscriber device 40-1. The subscriber device40-1 communicates with a communication destination device via along-distance line P1. A mobile base station 46-2 is connected to thesubscriber device 40-2. In FIG. 14 , a plurality of subscriber devices40-2 are connected to one transmission line 50-1 by a power splitter 55.The subscriber device 40-2 communicates with a communication destinationdevice via a medium-distance line P2. A user 46-3 who uses thesubscriber device 40-3 is a user who performs medium-distance ormedium-speed communication. One or more communication devices of theuser 46-3 communicate with a communication destination device through amedium-distance line P3 via the subscriber device 40-3. Optical signalsof the long-distance line P1, the medium-distance line P2, and themedium-distance line P3 are wavelength-multiplexed and transmittedthrough the multiplex communication transmission line 90 connected to acore network (NW). The electrical processing unit 84 has a DSP functionfor long-distance/high-speed access, a mobile fronthaul processingfunction, an error correction function, and the like.

An operation of the optical SW 10 h will be described with reference toFIGS. 13 and 14 . The optical SW 10 h outputs an uplink optical signaltransmitted by the subscriber device 40-1 to the electrical processingunit 84. The O/E conversion unit 85 of the electrical processing unit 84converts the input optical signal into an electrical signal. Theprocessing execution unit 86 performs DSP processing forlong-distance/high-speed access on the converted electrical signal. TheE/O conversion unit 87 converts the electrical signal subjected to theDSP processing into an optical signal and outputs the optical signal tothe optical SW 10 h. The wavelength after conversion may be the same asor different from the wavelength when input to the electrical processingunit 84. The optical SW 10 h outputs the optical signal input from theelectrical processing unit 84 to the multiplex communicationtransmission line 90 from the port 11-2.

The optical SW 10 h receives a downlink optical signal addressed to thesubscriber device 40-1 transmitted through the multiplex communicationtransmission line 90. The optical SW 10 h outputs the received downlinkoptical signal from the port 12-1 to the electrical processing unit 84according to a combination of the input port 51-2 and the wavelength.The O/E conversion unit 85 of the electrical processing unit 84 convertsthe input optical signal into an electrical signal, and the processingexecution unit 86 performs DSP processing for long-distance/high-speedaccess on the converted electrical signal. The E/O conversion unit 87converts the electrical signal subjected to the DSP processing into anoptical signal and outputs the optical signal to the optical SW 10 h.The wavelength after conversion of the optical signal may be the same asor different from the wavelength when input to the electrical processingunit 84. The optical SW 10 h outputs the optical signal input from theelectrical processing unit 84 to the port 11-1 connected to thesubscriber device 40-1.

In the above example, the configuration has been described in which theelectrical processing unit 84 modulates a multiplexed electrical signalwith the same signal and converts the modulated electrical signal intoan optical signal having a plurality of wavelengths. The electricalprocessing unit 84 may be configured to convert a multiplexed ordemultiplexed electrical signals into one or more optical signals(optical signals modulated with the same signal or different signals)having one or more wavelengths.

An optical signal transmitted and received by the subscriber device 40-2is also processed in the same manner as an optical signal transmittedand received by the subscriber device 40-1 described above. However, theprocessing execution unit 86 performs mobile fronthaul processing on theoptical signal transmitted and received by the subscriber device 40-2.The processing execution unit 86 determines signal processing to beperformed on the electrical signal on the basis of any informationincluded in the electrical signal.

On the other hand, the optical SW 10 h outputs an uplink optical signalinput from the subscriber device 40-3 to the multiplex communicationtransmission line 90 from the port 11-2. The optical SW 10 h receives adownlink optical signal addressed to the subscriber device 40-3transmitted through the multiplex communication transmission line 90,and outputs the downlink optical signal to the port 11-1 connected tothe subscriber device 40-3 according to a combination of the port 11-2to which the optical signal is input and the wavelength.

FIG. 15 is a diagram illustrating a configuration example of an opticalSW 10 i that monitors an optical signal before performing WDMtransmission. In the same figure, the same constituents as those of theoptical SW 10 e illustrated in FIG. 6 are denoted by the same referencenumerals, and description thereof will be omitted. The difference fromFIG. 6 is that a monitoring unit 60 is provided between the port 11-2and the WDM device 80. The transmission line 50-2 connected to the port11-2 includes the monitoring unit 60. In the same figure, only threemonitoring units 60 are illustrated. A specific configuration of themonitoring unit 60 is as illustrated in FIG. 2 . The optical signalsoutput from the ports 11-2 are multiplexed and output by the WDM device80 via the monitoring unit 60. The WDM device 80 demultiplexes theoptical signal received via the multiplex communication transmissionline 90 according to wavelengths, and inputs the demultiplexed opticalsignals to the monitoring units 60, respectively. The monitoring unit 60generates monitoring information based on a monitoring result andoutputs the generated monitoring information. An example of an outputdestination of the monitoring information is the control unit 20.

Next, an access topology to the optical SW will be described withreference to FIGS. 16 to 25 .

FIG. 16 is a diagram illustrating a passive double star (PDS) typeaccess topology using time division multiplexing. As an optical SW 1001,the above-described optical SWs 10 a to 10 i may be used. The optical SW1001 includes ports 11-1-1 to 11-1-P and ports 11-2-1 to 11-2-Q. Thetransmission line 50-1 connected to the port 11-1-p (where p is aninteger of 1 or more and P or less) will also be referred to as atransmission line 50-1-p, and the transmission line 50-2 connected tothe port 11-2-q (where q is an integer of 1 or more and Q or less) willalso be referred to as a transmission line 50-2-q. In FIG. 16 , the port11-2-q is connected to a ground #q via the transmission line 50-2-q.

A power splitter 56 is provided in the transmission line 50-1-p. Np(where Np is an integer of 2 or more) subscriber devices 40-p areconnected to the power splitter 56 in a star form. The Np subscriberdevices 40-p will be referred to as subscriber devices 40-p-1 to40-p-Np, and the transmission line 50-1-p between the subscriber device40-p-np (where np is an integer of 1 or more and Np or less) and thepower splitter 56 will be referred to as 50-1-p-np. The subscriberdevices 40-p-1 to 40-p-Np use the same wavelength on the basis of timedivision multiplexing. A wavelength used for an uplink optical signal isdifferent from a wavelength used for a downlink optical signal.

The optical SW 1001 receives a downlink optical signal subjected to timedivision multiplexing and having the wavelength λ₁ addressed to thesubscriber devices 40-p-1 to 40-p-Np from the port 11-2-q. The opticalSW 1001 outputs the received downlink optical signal from the port11-1-p that is an output destination according to the combination of theport 11-2-q and the wavelength λ₁. The power splitter 56 receives thetime-division-multiplexed downlink optical signal from the transmissionline 50-1-p, branches the received optical signal, and outputs thebranched optical signals to the transmission lines 50-1-p-1 to50-1-p-Np. The subscriber devices 40-p-1 to 40-p-Np receive thetime-division-multiplexed optical signals and select downlink opticalsignals addressed to the own devices from the received optical signals.

The subscriber devices 40-p-1 to 40-p-Np transmittime-division-multiplexed uplink optical signals having the samewavelength λ₂ according to time division multiple access (TDMA). Thepower splitter 56 receives the uplink optical signal having thewavelength λ₂ from each of the transmission lines 50-1-p-1 to 50-1-p-Np,time-divisionally multiplexes the input optical signals, and outputs thetime-division-multiplexed optical signal to the transmission line50-1-p. The optical SW 1001 outputs the time-division-multiplexed uplinkoptical signal from the port 11-2-q according to the combination of theport 11-1-p and the wavelength λ₂.

A PDS type access topology may be applied to any one or more of thetransmission lines 50-1-1 to 50-1-p.

FIG. 17 is a diagram illustrating a PDS type access topology usingwavelength multiplexing. As an optical SW 1002, the above-describedoptical SWs 10 a to 10 i may be used. The optical SW 1002 is connectedto one or more WDM devices 81. The WDM device 81 multiplexes downlinkoptical signals having different wavelengths output from the pluralityof ports 11-1 and outputs the multiplexed optical signal to themultiplex communication transmission line 91. The WDM device 81demultiplexes an uplink wavelength-multiplexed optical signal receivedvia the multiplex communication transmission line 91, and inputs thedemultiplexed optical signals to different ports 11-1. The powersplitter 56 is provided in the multiplex communication transmission line91. N (where N is an integer of 2 or more) subscriber devices 40 areconnected to the power splitter 56 in a star form. The subscriber device40 and the power splitter 56 are connected via a transmission line 92.The plurality of subscriber devices 40 connected to the power splitter56 transmit and receive optical signals having different wavelengths.

In FIG. 17 , the ports 11-1-p to 11-1-(p+N) of the optical SW 1002 areconnected to the WDM device 81 via the transmission lines 50-1 (where pand N are integers of 1 or more, and p+N is an integer of P or less).Subscriber devices 40-p to 40-(p+N) are connected to the power splitter56.

The optical SW 1002 receives a downlink optical signal addressed to thesubscriber device 40-(p+n) having the wavelength λ_(1(q+n)) from theport 11-2-(q+n) (where q is an integer of 1 or more, and n is an integerof 0 or more and N or less). FIG. 17 illustrates an example in a casewhere q=1. The optical SW 1002 routes the downlink optical signal havingthe wavelength λ_(1(1+n)) input from the port 11-2-(q+n) to the port11-1-(p+n) that is an output destination corresponding to a combinationof the port 11-2-(q+n) and the wavelength λ_(1(1+n)). Consequently, theoptical SW 1002 routes the downlink optical signal having the wavelengthλ₁₁ input from the port 11-2-1 to the port 11-1-p, and routes thedownlink optical signal having the wavelength λ₁₂ input from the port11-2-2 to the port 11-1-(p+1).

The WDM device 81 multiplexes the downlink optical signals having thewavelengths λ₁₁ to λ_(1N) respectively output from the ports 11-1-p to11-1-(p+N) and outputs the multiplexed optical signal to the multiplexcommunication transmission line 91. The power splitter 56 receives thewavelength-multiplexed downlink optical signal from the multiplexcommunication transmission line 91, branches the received downlinkoptical signal without any change, and outputs the branched opticalsignals to the transmission lines 92 connected to the respectivesubscriber devices 40-p to 40-(p+N). The subscriber devices 40-p to40-(p+N) receive the wavelength-multiplexed downlink optical signals,and select downlink optical signals having wavelengths used by the owndevices from the received optical signals.

The subscriber device 40-(p+n) transmits an uplink optical signal havinga wavelength λ_(2(1+n)). The power splitter 56 receives an uplinkoptical signal from each of the subscriber devices 40-p to 40-(p+N) viathe transmission line 92, performs wavelength multiplexing on thereceived uplink optical signal having each of the wavelengths λ₂₁ toλ_(2(1+N)), and outputs the multiplexed optical signal to the multiplexcommunication transmission line 91. The WDM device 81 receives thewavelength-multiplexed uplink optical signal from the multiplexcommunication transmission line 91 and performs wavelength separation.The WDM device 81 inputs uplink optical signals having the wavelengthλ_(2(1+n)) to the port 11-1-(p+n). The optical SW 1002 outputs theuplink optical signal having the wavelength λ_(2(1+n)) from the port11-2-(q+n) that is an output destination corresponding to a combinationof the input port 11-1-(p+n) and the wavelength λ_(2(1+n)).Consequently, the uplink optical signal having the wavelength λ₂₁transmitted by the subscriber device 40-p is input from the port 11-1-pand output from the port 11-2-1. The uplink optical signal having thewavelength λ₂₂ transmitted by the subscriber device 40-(p+1) is inputfrom the port 11-1-(p+1) and output from the port 11-2-2. As illustratedin FIG. 18 , a WDM device may be provided at a subsequent stage withrespect to the optical SW.

FIG. 18 is a diagram illustrating a PDS type access topology in whichwavelength multiplexing is used and a WDM device is provided at asubsequent stage with respect to an optical SW. As an optical SW 1003,the above-described optical SWs 10 a to 10 i may be used. A port 11-2-q(where q is an integer between 1 and Q) of the optical SW 1003 isconnected to a WDM device 97 via a transmission line 50-2-q. The WDMdevice 97 is connected to a ground #n (where n is an integer of 1 ormore and N or less) via a transmission line 50-2-q-n. A power splitter56 is provided in the transmission line 50-1-p connected to the port11-1-p of the optical SW 1003. N subscriber devices 40-p-1 to 40-p-N areconnected to the power splitter 56 in a star form.

The WDM device 97 receives a downlink optical signal having a wavelengthλ_(1n) addressed to the subscriber device 40-p-n transmitted from theground #n from the transmission line 50-2-q-n. The WDM device 97 inputs,to the optical SW 1003, a wavelength-multiplexed signal obtained bymultiplexing the downlink optical signals having λ₁₁ to λ₁N respectivelyinput from the ground #1 to the ground #N. The optical SW 1003 outputsthe wavelength-multiplexed downlink signal input from the port 11-2-qfrom the port 11-1-p that is an output destination. The power splitter56 branches the wavelength-multiplexed signal input from thetransmission line 50-1-p and outputs the branched signals to thetransmission lines 50-1-p-1 to 50-1-p-N. The subscriber devices 40-p-1to 40-p-N receive the wavelength-multiplexed signals and select downlinkoptical signals addressed to the own devices from the received opticalsignals. Consequently, the subscriber device 40-p-n receives the opticalsignal having the wavelength λ_(1n) from the ground #n.

The subscriber device 40-p-n transmits an uplink optical signal having awavelength λ_(2n). The power splitter 56 receives uplink optical signalshaving wavelengths λ₂₁ to λ_(2N) from the respective subscriber devices40-p-1 to 40-p-N via the transmission lines 50-1-p-1 to 50-1-p-N. Thepower splitter 56 outputs a wavelength-multiplexed signal obtained bywavelength-multiplexing the uplink optical signals having thewavelengths λ₂₁ to λ_(2N) to the transmission line 50-1-p. The opticalSW 1003 receives, from the port 11-1-p, the wavelength-multiplexedsignal obtained by wavelength-multiplexing the uplink optical signalshaving the wavelengths λ₂₁ to λ_(2N). The optical SW 1003 outputs thewavelength-multiplexed uplink signal from the output destination port11-2-q to the transmission line 50-2-q. The WDM device 97 receives thewavelength-multiplexed uplink optical signal from the transmission line50-2-q and performs wavelength separation. The WDM device 97 outputs theuplink optical signal having a wavelength λ_(2n) to the transmissionline 50-2-n connected to the ground #n. Consequently, the optical signalhaving the wavelength λ_(2n) transmitted by the subscriber device 40-p-nis transmitted to the ground #n.

FIG. 19 is a diagram illustrating a bus type access topology using timedivision multiplexing. As an optical SW 1004, the above-describedoptical SWs 10 a to 10 i may be used. The access topology illustrated inFIG. 19 is different from the access topology illustrated in FIG. 16 inthat a plurality of bus type subscriber devices 40-p-1 to 40-p-Np areconnected to the transmission line 50-1-p. One or more power splitters55 are provided in the transmission line 50-1-p. The power splitter 55to which the subscriber device 40-p-n (where n is an integer of 1 ormore and Np−1 or less) is connected will be referred to as a powersplitter 55-n.

The subscriber devices 40-p-1 to 40-p-Np use the same wavelength on thebasis of time division multiplexing. A wavelength used for an uplinkoptical signal is different from a wavelength used for a downlinkoptical signal. The transmission line 50-2-1 connected to the ground #1transmits a time-division-multiplexed downlink optical signals havingthe wavelength λ1 addressed to the respective subscriber devices 40-p-1to 40-p-Np. The optical SW 1004 receives, from the port 11-2-1, thetime-division-multiplexed downlink optical signal having the wavelengthλ₁ transmitted through the transmission line 50-2-1. The optical SW 1004routes the received downlink optical signal to the port 11-1-p that isan output destination corresponding to a combination of the port 11-2-1(or the ground #1) and the wavelength λ₁. The optical SW 1004 outputsthe time-division-multiplexed downlink optical signal having thewavelength λ₁ from the port 11-1-p to the transmission line 50-1-p. Thepower splitter 55-n branches the time-division-multiplexed downlinkoptical signal from the transmission line 50-1-p and outputs thebranched downlink optical signal to the subscriber device 40-p-n. Thesubscriber devices 40-p-1 to 40-p-Np receive time-division-multiplexeddownlink optical signals and select downlink optical signals addressedto the own devices from the received downlink optical signals.

The subscriber devices 40-p-1 to 40-p-Np transmittime-division-multiplexed uplink optical signals having the samewavelength λ₂ according to TDMA. Each power splitter 55-ntime-divisionally multiplexes the uplink optical signal having thewavelength λ₂ input from the subscriber device 40-p-n with the uplinkoptical signal transmitted through the transmission line 50-1-p. Theoptical SW 1004 receives the time-division-multiplexed uplink opticalsignal from the port 11-1-p, routes the signal to the port 11-2-1 thatis an output destination corresponding to a combination of the port11-1-p and the wavelength λ₂, and outputs the signal to the transmissionline 50-2-1 connected to the ground #1.

The bus type access topology may be applied to any one or more of thetransmission lines 50-1-1 to 50-1-p.

FIG. 20 is a diagram illustrating a bus type access topology usingwavelength multiplexing. As an optical SW 1005, the above-describedoptical SWs 10 a to 10 i may be used. The access topology illustrated inFIG. 19 is different from the access topology illustrated in FIG. 17 inthat a plurality of bus type subscriber devices 40-p to 40-(p+N) areconnected to the multiplex communication transmission line 91. Thesubscriber devices 40-p to 40-(p+N) transmit and receive optical signalshaving different wavelengths. One or more power splitters 55 areprovided in the multiplex communication transmission line 91. The powersplitter 55 to which the subscriber device 40-(p+n) (where n is aninteger of 0 or more and N−1 or less, and N is an integer of 1 or more)is connected will be referred to as a power splitter 55-(p+n).

Similarly to the optical SW 1002 illustrated in FIG. 17 , the optical SW1005 receives a downlink optical signal addressed to the subscriberdevice 40-(p+n) having the wavelength λ_(1(1+n)) from the port11-2-(q+n) (where q is an integer of 1 or more, and n is an integer of 0or more and N or less). FIG. 20 illustrates an example in a case whereq=1. The optical SW 1005 routes the downlink optical signal having thewavelength λ_(1(1+n)) input from the port 11-2-(q+n) to the port11-1-(p+n) that is an output destination corresponding to a combinationof the port 11-2-(q+n) and the wavelength λ_(1(1+n)).

The WDM device 81 multiplexes the downlink optical signals having thewavelengths λ₁₁ to λ_(1N) respectively output from the ports 11-1-p to11-1-(p+N) and outputs the multiplexed optical signal to the multiplexcommunication transmission line 91. The power splitter 55-(p+n) branchesthe wavelength-multiplexed downlink optical signal from the multiplexcommunication transmission line 91 and outputs the branched downlinkoptical signal to the subscriber device 40-(p+n). The subscriber devices40-p to 40-(p+N) receive the wavelength-multiplexed downlink opticalsignals and select downlink optical signals addressed to the own devicesfrom the received downlink optical signals.

The subscriber device 40-(p+n) transmits an uplink optical signal havinga wavelength λ_(2(1+n)). Each power splitter 55-(p+n) multiplexes theuplink optical signal having the wavelength λ_(2(1+n)) input from thesubscriber device 40-(p+n) with the uplink optical signal having thewavelengths λ_(2(2+n)) to λ_(2N) transmitted through the multiplexcommunication transmission line 91. The WDM device 81 receives thewavelength-multiplexed uplink optical signal from the multiplexcommunication transmission line 91 and separates the optical signal intouplink optical signals having wavelengths λ₂₁ to λ_(2N). The WDM device81 inputs an uplink optical signal having the wavelength λ_(2(1+n)) tothe port 11-1-(p+n). Similarly to the optical SW 1002 illustrated inFIG. 16 , the optical SW 1005 outputs the uplink optical signal havingthe wavelength λ_(2(1+n)) from the port 11-2-(q+n) that is an outputdestination corresponding to a combination of the input port 11-1-(p+n)and the wavelength λ_(2(1+n)). Consequently, the uplink optical signalhaving the wavelength λ₂₁ transmitted by the subscriber device 40-p isinput from the port 11-1-p and output from the port 11-2-1. The uplinkoptical signal having the wavelength λ₂₂ transmitted by the subscriberdevice 40-(p+1) is input from the port 11-1-(p+1) and output from theport 11-2-2. As illustrated in FIG. 21 , a WDM device may be provided ata subsequent stage with respect to the optical SW.

FIG. 21 is a diagram illustrating a bus type access topology in whichwavelength multiplexing is used and a WDM device is provided at asubsequent stage with respect to an optical SW. As an optical SW 1006,the above-described optical SWs 10 a to 10 i may be used. In FIG. 21 ,the same constituents as those in FIG. 18 are denoted by the samereference numerals. A port 11-2-q (where q is an integer 1 or more and Qor less) of the optical SW 1006 is connected to a WDM device 97 via atransmission line 50-2-q. The WDM device 97 is connected to a ground #n(where n is an integer of 1 or more and N or less, and N is an integerof 2 or more) via a transmission line 50-2-q-n. One or more powersplitters 55 are provided in the transmission line 50-1-p connected tothe port 11-1-p (where p is an integer of 1 or more and P or less) ofthe optical SW 1006. The power splitter 55 to which the subscriberdevice 40-p-n is connected will be referred to as a power splitter 55-n.

The WDM device 97 receives a downlink optical signal having a wavelengthλ_(1n) addressed to the subscriber device 40-p-n transmitted from theground #n from the transmission line 50-2-q-n. The WDM device 97 inputs,to the optical SW 1006, a wavelength-multiplexed signal obtained bymultiplexing downlink optical signals having wavelengths λ₁₁ to λ_(1N)respectively input from the ground #1 to the ground #N. The optical SW1006 outputs the wavelength-multiplexed downlink signal input from theport 11-2-q from the port 11-1-p that is an output destination. Thepower splitter 55-n branches the wavelength-multiplexed downlink signalfrom the transmission line 50-1-p and outputs the branchedwavelength-multiplexed downlink signal to the subscriber device 40-p-n.The subscriber devices 40-p-1 to 40-p-N select downlink optical signalsaddressed to the own devices from the received wavelength-multiplexeddownlink signals. Consequently, the subscriber device 40-p-n receivesthe optical signal having the wavelength λ_(1n) from the ground #n.

The subscriber device 40-p-n transmits an uplink optical signal having awavelength λ_(2n). Each power splitter 55-n wavelength-multiplexes theuplink optical signal having the wavelength λ_(2n) input from thesubscriber device 40-p-n with the uplink optical signal transmittedthrough the transmission line 50-1-p. The optical SW 1006 receives, fromthe port 11-1-p, a wavelength-multiplexed signal obtained bywavelength-multiplexing the uplink optical signals having thewavelengths N₂₁ to λ₂N. The optical SW 1006 outputs thewavelength-multiplexed uplink signal from the port 11-2-q that is anoutput destination to the transmission line 50-2-q. The WDM device 97receives a wavelength-multiplexed signal from the transmission line50-2-q and performs wavelength separation. The WDM device 97 outputs anuplink optical signal having the wavelength λ_(2n) to the transmissionline 50-2-q-n connected to the ground #n. Consequently, the opticalsignal having the wavelength 2 n transmitted by the subscriber device40-p-n is transmitted to the ground #n.

FIG. 22 is a diagram illustrating a loop type access topology. As anoptical SW 1007, the above-described optical SWs 10 a to 10 i may beused. Some ports 11-1-p 1 to 11-1-pN (where p1<pN, p1 is an integer of 1or more, and pN is an integer of P or less) of the optical SW 1007 areconnected to a WDM access ring network 31 that transmits optical signalshaving a plurality of wavelengths. Optical signals having severalwavelengths used in the WDM access ring network 31 are transmitted tothe subscriber device 40 that is a communication destination or a higherNW via the optical SW 1007. In the topology illustrated in FIG. 22 , aWDM multiplexer/demultiplexer is not used, and opposing subscriberdevices 40 are connected via two transmission lines to performcommunication.

The WDM access ring network 31 is a network in which R add/drop nodes 32are connected via a transmission line 53. FIG. 21 illustrates an exampleof R=4. The R add/drop nodes 32 will be referred to as add/drop nodes32-1 to 32-R, and the transmission line 53 between the add/drop node32-r (where r is an integer of 1 or more and R or less) and the add/dropnode 32-(r+1) will be referred to as a transmission line 53-r. However,the add/drop node 32-(R+1) is regarded as an add/drop node 32-1. Theadd/drop node 32-1 is connected to the port 11-1-pn (where pn is aninteger of p1 or more and pN or less) of the optical SW 1007 via thetransmission line 50-1-pn.

The add/drop node 32 includes a demultiplexing unit 33, an optical SW34, and a multiplexing unit 35. The demultiplexing unit 33 of theadd/drop node 32-r (where r is an integer of 2 or more and R or less)demultiplexes the wavelength-multiplexed optical signal input from thetransmission line 53-(r-1), and outputs an optical signal obtained bythe demultiplexing to the optical SW 34. The optical SW 34 is connectedto one or more subscriber devices 40. In the drawing, only onesubscriber device 40 connected to the optical SW 34 is illustrated. Theoptical SW 34 drops an optical signal having a wavelength correspondingto the own node among optical signals input from the demultiplexing unit33. The optical receiver 43 of the subscriber device 40 receives theoptical signal dropped by the optical SW 34. The optical SW 34 receivesan optical signal transmitted from the optical transmitter 42 of thesubscriber device 40, and outputs the received optical signal and theoptical signal that has not been dropped to the multiplexing unit 35.The multiplexing unit 35 of the add/drop node 32-r multiplexes theoptical signals input from the optical SW 34 and outputs the multiplexedoptical signal to the transmission line 53-r. The optical SW 34 of theadd/drop node 32-1 drops an optical signal having a wavelengthcorresponding to the own node among the optical signals demultiplexed bythe demultiplexing unit 33, and inputs the optical signal having eachwavelength to the transmission line 50-1-pn 1 (where pn1=1, 3, 5, . . ., and p(N−1)). The port 11-1-pn 1 of the optical SW 1007 receives theoptical signal dropped by the add/drop node 32-1 from the transmissionline 50-1-pn 1. The optical SW 34 of the add/drop node 32-1 receives theoptical signal output from the port 11-1-pn 2 (where pn2=2, 4, 6, . . ., and pN) by the optical SW 1007 from the transmission line 50-1-pn 2,and outputs the received optical signal and the optical signal that hasnot been dropped to the multiplexing unit 35.

Consequently, an ONU #1 that is the subscriber device 40 connected tothe add/drop node 32-4 of the WDM access ring network 31 and an ONU #2that is the subscriber device 40 connected to the port 11-2-1 and theport 11-2-2 of the optical SW 1007 perform communication as follows.

The ONU #1 transmits an optical signal having the wavelength λ₁ to theadd/drop node 32-4. The multiplexing unit 35 of the add/drop node 32-4multiplexes the optical signal having the wavelength λ₁ input by theoptical SW 34 and the optical signal not dropped by the optical SW 34,and outputs the multiplexed signal to the add/drop node 32-1. Theoptical SW 34 of the add/drop node 32-1 drops the optical signal havingthe wavelength λ₁ demultiplexed by the demultiplexing unit 33 andoutputs the optical signal that has not been dropped to the multiplexingunit 35. The port 11-1-p 1 of the optical SW 1007 receives the opticalsignal having the wavelength λ₁ dropped by the add/drop node 32-1 fromthe transmission line 50-1-p 1. The optical SW 1007 outputs the opticalsignal having the wavelength λ₁ input from the port 11-1-p 1 from theport 11-2-1. The optical receiver 43 of the ONU #2 receives the opticalsignal having the wavelength λ₁ transmitted through the transmissionline 50-2-1.

The optical transmitter 42 of the ONU #2 transmits a downlink opticalsignal having the wavelength λ₂. The port 11-2-2 of the optical SW 1007receives the optical signal transmitted by the ONU #2 from thetransmission line 50-2-2. The optical SW 1007 outputs the downlinkoptical signal having the wavelength λ₂ input from the port 11-2-2 fromthe port 11-1-p 2. The optical SW 34 of the add/drop node 32-1 receivesthe optical signal having the wavelength λ₂ output from the optical SW1007 from the transmission line 50-1-p 2, and outputs the receivedoptical signal and the optical signal that has not been dropped to themultiplexing unit 35. The optical signal having the wavelength λ₂ isinput to the add/drop node 32-4 via the add/drop nodes 32-2 and 32-3.The optical SW 34 of the add/drop node 32-4 drops the optical signalhaving the wavelength λ₂. The optical receiver 43 of the ONU #1 receivesthe optical signal having the wavelength λ₂ dropped by the add/drop node32-4.

FIG. 23 is a diagram illustrating a loop type access topology using aWDM multiplexer/demultiplexer. As an optical SW 1008, theabove-described optical SWs 10 a to 10 i may be used. The accesstopology illustrated in FIG. 23 is different from the access topologyillustrated in FIG. 22 in that the optical SW 1008 and the WDM accessring network 31 are connected via a WDM device 81 and a WDM device 89.

The add/drop node 32-1 of the WDM access ring network 31 and the WDMdevice 89 are connected via transmission lines 93-1 to 93-N (where N isan integer of 2 or more). The WDM device 89 receives an uplink opticalsignal having the wavelength λ_(n1) from the transmission line 93-n ₁(where n₁=1, 3, 5, . . . , and N−1), and outputs a multiplexed signalobtained by multiplexing the received uplink optical signals to themultiplex communication transmission line 91. The WDM device 89demultiplexes the downlink wavelength-multiplexed optical signalreceived via the multiplex communication transmission line 91, andinputs the demultiplexed downlink optical signal having the wavelengthλ_(n2) to the transmission line 93-n ₂ (where n₂=2, 4, 6, . . . , andN).

The WDM device 81 demultiplexes the uplink wavelength-multiplexedoptical signal received via the multiplex communication transmissionline 91, and inputs the demultiplexed uplink optical signal having thewavelength λ₁ to the port 11-1-n ₁. The WDM device 81 receives thedownlink optical signal having the wavelength λ_(n2) output from each ofthe ports 11-1-pn 2, multiplexes the received downlink signals, andoutputs the multiplexed signal to the multiplex communicationtransmission line 91.

Consequently, the ONU #1 that is the subscriber device 40 connected tothe add/drop node 32-4 of the WDM access ring network 31 and the ONU #2that is the subscriber device 40 connected to the port 11-2-1 and theport 11-2-2 of the optical SW 1008 perform communication as follows. Acase of N=18 will be described as an example.

The ONU #1 transmits the uplink optical signal having the wavelength λ₁to the add/drop node 32-4. Another ONU transmits uplink optical signalshaving wavelengths λ₃ and λ₅ to the add/drop node 32-4. The optical SW34 of the add/drop node 32-4 receives the optical signals havingwavelengths λ₁, λ₃, and λ₅. The multiplexing unit 35 of the add/dropnode 32-4 multiplexes the optical signals having the wavelengths λ₁, λ₃,and λ₅ input by the optical SW 34 and the optical signal not dropped bythe optical SW 34, and outputs the multiplexed signal to the add/dropnode 32-1. The optical SW 34 of the add/drop node 32-1 drops the opticalsignals having the wavelengths λ₁, λ₃, λ₅, . . . , and λ₁₇ demultiplexedby the demultiplexing unit 33, and outputs an optical signal that hasnot been dropped to the multiplexing unit 35. The WDM device 89 outputs,to the multiplex communication transmission line 91, a multiplexedsignal obtained by multiplexing the uplink optical signals having thewavelengths λ₁, λ₃, λ₅, . . . , and λ₁₇ respectively input from thetransmission lines 93-1, 93-3, 93-5, . . . , and 93-17.

The WDM device 81 receives the wavelength-multiplexed uplink opticalsignal from the multiplex communication transmission line 91 andperforms wavelength separation. The WDM device 81 inputs the uplinkoptical signals having the wavelengths λ₁, λ₃, λ₅, . . . , and λ₁₇ tothe ports 11-1-p 1, 11-1-p 3, 11-1-p 5, . . . , and 11-1-p 17 of theoptical SW 1008, respectively. The optical SW 1008 outputs the uplinkoptical signal having the wavelength λ₁ from the port 11-2-1 that is anoutput destination. The optical receiver 43 of the ONU #2 receives theoptical signal having the wavelength λ₁ transmitted through thetransmission line 50-2-1.

The optical transmitter 42 of the ONU #2 transmits a downlink opticalsignal having the wavelength λ₂. The port 11-2-2 of the optical SW 1008receives the optical signal transmitted by the ONU #2 from thetransmission line 50-2-2. The optical SW 1008 outputs the downlinkoptical signal having the wavelength λ₂ input from the port 11-2-2 fromthe port 11-1-p 2. the optical SW 1008 outputs downlink optical signalshaving wavelengths λ₄, λ₆, . . . , and λ₁₈ respectively input from theports 11-2-4, 11-2-6, . . . , and 11-2-18 from the ports 11-1-p 4,11-2-p 6, . . . , and 11-2-p 18.

The WDM device 81 outputs, to the multiplex communication transmissionline 91, a wavelength-multiplexed signal obtained by multiplexing thedownlink optical signals having the wavelengths λ₂, λ₄, λ₆, . . . , andhis respectively output from the ports 11-1-p 2, 11-1-p 4, 11-1-p 6, . .. , and 11-1-p 18. The WDM device 89 separates thewavelength-multiplexed signal transmitted through the multiplexcommunication transmission line 91, and outputs the downlink opticalsignals having the wavelengths λ₂, λ₄, λ₆, . . . , and λ₁₈ obtainedthrough the separation to the transmission lines 93-2, 93-4, 93-6, . . ., and 93-18, respectively. The optical SW 34 of the add/drop node 32-1receives the optical signals having the wavelengths N₂, N₄, λ₆, . . . ,and λ_(1s) output from the WDM device 89 from the transmission lines93-2, 93-4, 93-6, . . . , and 93-18, respectively, and outputs thereceived optical signals and the optical signal that has not beendropped to the multiplexing unit 35. The multiplexing unit 35multiplexes the optical signals input from the optical SW 34 and outputsthe multiplexed optical signal to the transmission line 53-1.

The demultiplexing unit 33 of the add/drop node 32-2 demultiplexes theoptical signal input from the transmission line 53-1 and outputs thedemultiplexed signals to the optical SW 34. The optical SW 34 drops theoptical signals having wavelengths λ₁₄, λ₁₆, and λ₁₈ corresponding tothe own node. The optical signals having the wavelengths λ₁₄, λ₁₆, andλ₁₈ are transmitted to the optical receivers 43 of the subscriberdevices 40 respectively corresponding to the wavelengths. The optical SW34 of the add/drop node 32-2 receives the optical signals having thewavelengths λ₁₃, λ₁₅, and λ₁₇ respectively transmitted by the opticaltransmitters 42 of the subscriber devices 40, and outputs the receivedoptical signals and the optical signal that has not been dropped to themultiplexing unit 35. The multiplexing unit 35 multiplexes the opticalsignals input from the optical SW 34 and outputs the multiplexed opticalsignals to the transmission line 53-2.

The add/drop node 32-3 operates similarly to the add/drop node 32-2.However, the optical SW 34 of the add/drop node 32-3 drops the opticalsignals having the wavelengths λ₈, λ₁₀, and λ₁₂ corresponding to the ownnode, and inputs the optical signals having the wavelengths λ₇, λ₉, andλ₁₁. The demultiplexing unit 33 of the add/drop node 32-4 demultiplexesthe wavelength-multiplexed optical signal input from the transmissionline 53-3 and outputs the demultiplexed signals to the optical SW 34.The optical SW 34 of the add/drop node 32-4 drops the optical signalshaving wavelengths λ₂, λ₄, and λ₆ corresponding to the own node. Theoptical receiver 43 of the ONU #1 receives the optical signal having thewavelength λ₂ dropped by the optical SW 34 of the add/drop node 32-4.

FIG. 24 is a diagram illustrating an access topology in which two accesssurfaces form one loop. As an optical SW 1009 a and an optical SW 1009b, the above-described optical SWs 10 a to 10 i may be used. The opticalSW 1009 a and the optical SW 1009 b are collectively referred to as anoptical SW 1009. Two ports 11-1 of the optical SW 1009 are connected toboth ends of one transmission line 54. One or more power splitters 57are connected to the transmission line 54. The power splitter 57 isconnected to the optical transmitters 42 of the one or more subscriberdevices 40 via the multiplexer 82 and the optical SW 95, and isconnected to the optical receivers 43 of the one or more subscriberdevices 40 via the demultiplexer 83 and the optical SW 96. Each of thesubscriber devices 40 transmits and receives optical signals havingdifferent wavelengths.

The transmission line 54 connected to the optical SW 1009 a will bereferred to as a transmission line 54 a, the two ports 11-1 connected tothe transmission line 54 a will be referred to as ports 11 a-1-p 1 and11 a-1-p 2, the transmission line 54 connected to the optical SW 1009 bwill be referred to as a transmission line 54 b, and the two ports 11-1connected to the transmission line 54 b will be referred to as ports 11b-1-p 1 and 11 b-1-p 2. The N (where N is an integer of 1 or more) powersplitters 57 connected to the transmission line 54 a will be referred toas power splitters 57 a-1 to 57 a-N, and the M (M is an integer of 1 ormore) power splitters 57 connected to the transmission line 54 b will bereferred to as power splitters 57 b-1 to 57 b-M. The multiplexer 82 andthe demultiplexer 83 connected to the power splitters 57 a-n (where n isan integer of 1 or more and N or less) will be respectively referred toas a multiplexer 82 a-n and a demultiplexer 83 a-n, and the multiplexer82 and the demultiplexer 83 connected to the power splitters 57 b-m(where m is an integer of 1 or more and M or less) will be respectivelyreferred to as a multiplexer 82 b-m and a demultiplexer 83 b-m. Theoptical SW 95 connected to the multiplexer 82 a-n will be referred to asan optical SW 95 a-n, and the optical SW 96 connected to thedemultiplexer 83 a-n will be referred to as an optical SW 96 a-n. Theoptical SW 95 connected to the multiplexer 82 b-m will be referred to asan optical SW 95 b-m, and the optical SW 96 connected to thedemultiplexer 83 b-m will be referred to as an optical SW 96 b-m.

The optical SW 1009 a and the optical SW 1009 b are connected via atransmission line 54 c and a transmission line 54 d. The port 11-2 ofthe optical SW 1009 a connected to the transmission line 54 c will bereferred to as a port 11 a-2-q 1, and the port 11-2 of the optical SW1009 a connected to the transmission line 54 d will be referred to as aport 11 a-2-q 2. The port 11-2 of the optical SW 1009 b connected to thetransmission line 54 c will be referred to as a port 11 b-2-q 1, and theport 11-2 of the optical SW 1009 b connected to the transmission line 54d will be referred to as a port 11 b-2-q 2.

In the above configuration, the optical SW 95 b-m outputs opticalsignals having different wavelengths respectively transmitted by theoptical transmitters 42 of the subscriber devices 40 to the portsrespectively corresponding to wavelengths of the multiplexer 82 b-m. Themultiplexer 82 b-m receives optical signals having different wavelengthstransmitted by the optical transmitters 42 of the respective subscriberdevices 40 via the optical SW 95 b-m, and outputs awavelength-multiplexed optical signal obtained by multiplexing thereceived optical signals. The power splitter 57 b-m multiplexes thewavelength-multiplexed optical signal output from the multiplexer 82 b-mwith a wavelength-multiplexed optical signal transmitted through thetransmission line 54 b in a direction from the port 11 b-1-p 2 to theport 11 b-1-p 1, and outputs the multiplexed optical signal.

The port 11 b-1-p 1 of the optical SW 1009 b receives thewavelength-multiplexed optical signal from the transmission line 54 band outputs the wavelength-multiplexed optical signal from the port 11b-2-q 1. The port 11 a-2-q 1 of the optical SW 1009 a receives thewavelength-multiplexed optical signal output from the port 11 b-2-q 1 ofthe optical SW 1009 b from the transmission line 54 c. The optical SW1009 a outputs the wavelength-multiplexed optical signal input from theport 11 a-2-q 1 to the transmission line 54 a from the port 11 a-1-p 1.

The power splitter 57 a-n branches the wavelength-multiplexed opticalsignal transmitted through the transmission line 54 a in the directionfrom the port 11 a-1-p 1 to the port 11 a-1-p 2, and outputs thebranched wavelength-multiplexed optical signal to the demultiplexer 83a-n. The demultiplexer 83 a-n demultiplexes the wavelength-multiplexedoptical signal received from the power splitter 57 a-n, and outputs thedemultiplexed optical signal to the optical SW 96 a-n from a portcorresponding to a wavelength. The optical SW 96 a-n outputs the opticalsignal having each wavelength input from the demultiplexer 83 a-n to theoptical receiver 43 of the subscriber device 40 that receives theoptical signal having the wavelength.

On the other hand, the optical SW 95 a-n outputs optical signals havingdifferent wavelengths transmitted by the optical transmitters 42 of therespective subscriber devices 40 to ports corresponding to therespective wavelengths of the multiplexer 82 a-n. The multiplexer 82 a-nreceives the optical signals having different wavelengths transmitted bythe optical transmitters 42 of the respective subscriber devices 40 viathe optical SW 95 a-n, and outputs a wavelength-multiplexed opticalsignal obtained by multiplexing the input optical signals. The powersplitter 57 a-n multiplexes the wavelength-multiplexed optical signaloutput from the multiplexer 82 a-n with the wavelength-multiplexedoptical signal transmitted through the transmission line 54 a in thedirection from the port 11 a-1-p 1 to the port 11 a-1-p 2, and outputsthe wavelength-multiplexed optical signal.

The port 11 a-1-p 2 of the optical SW 1009 a receives thewavelength-multiplexed optical signal from the transmission line 54 aand outputs the wavelength-multiplexed optical signal from the port 11a-2-q 2. The port 11 b-2-q 2 of the optical SW 1009 b receives thewavelength-multiplexed optical signal output from the port 11 a-2-q 2 ofthe optical SW 1009 a from the transmission line 54 d. The optical SW1009 b outputs the wavelength-multiplexed optical signal input from theport 11 b-2-q 2 to the transmission line 54 b from the port 11 b-1-p 2.

The power splitter 57 b-m branches the wavelength-multiplexed opticalsignal transmitted through the transmission line 54 b in the directionfrom the port 11 b-1-p 2 to the port 11 b-1-p 1, and outputs thebranched wavelength-multiplexed optical signal to the demultiplexer 83b-m. The demultiplexer 83 b-m demultiplexes the wavelength-multiplexedoptical signal received from the power splitter 57 b-m, and outputs thedemultiplexed optical signals to the optical SW 96 b-m from portscorresponding to the wavelengths. The optical SW 96 b-m outputs theoptical signal having each wavelength input from the demultiplexer 83b-m to the optical receiver 43 of the subscriber device 40 that receivesthe optical signal having the wavelength.

Although FIG. 24 illustrates a case where the optical signal istransmitted counterclockwise, the optical signal may be transmittedclockwise, and a pair of left and right two cores may be used forredundancy.

FIG. 25 is a diagram illustrating a line type access topology. As anoptical SW 1100, the above-described optical SWs 10 a to 10 i may beused. The access topology illustrated in FIG. 25 is different from theaccess topology illustrated in FIG. 16 in that the monitoring unit 60 isconnected between a subscriber device 40-p and the optical SW 1100. Themonitoring unit 60 monitors an optical signal output from the subscriberdevice 40-p or an optical signal output from the port 11-1-p.

Next, a connection configuration in a case where the number of userconnections increases will be described. FIG. 26 is a diagramillustrating an example in which scalability of the optical SW isrequired. FIG. 26 illustrates N (where N is an integer of 1 or more)optical SWs 1010-1 to 1010-N. As the optical SWs 1010-1 to 1010-N, theabove-described optical SWs 10 a to 10 i may be used. FIG. 26illustrates an example of N=4. In the same figure, an ONU #np as thesubscriber device 40 is connected to the port 11-1-p of the optical SW1010-n (where n is an integer 1 or more and N or less). The port 11-2-qof the optical SW 1010-n is connected to an uplink. The uplink is atransmission line 50-2 connected to a higher network.

When the number of users becomes enormous and the number of ONUsincreases, the optical SW 1010 may exceed an accommodatable size. In thepresent embodiment, even in such a case, a function similar to that in acase where the number of users is small, for example, connection inwhich any uplink is selected or light return to any subscriber device isrealized by a connection configuration illustrated in FIG. 27 or 28 .

FIG. 27 is a diagram illustrating an example of optical SW scalabilityby a mesh configuration. Some ports 11-1 of the optical SW 1010 areconnected to the ONU via the transmission line 50-1, and some ports 11-2are connected to an uplink transmission line 50-2. Some ports 11-1 ofthe optical SW 1010 and some ports 11-2 of another optical SW 1010 areconnected via transmission lines 50-3. In the same figure, one opticalSW 1010 is connected to all the other optical SWs 1010.

The plurality of ports 11-1 of the optical SW 1010 will be referred toas ports 11-1-1, 11-1-2, 11-1-3, . . . , 11-1-p 1, 11-1-p 2, and 11-1-p3, and the plurality of ports 11-2 of the optical SW 1010 will bereferred to as ports 11-2-1, 11-2-2, 11-2-3, . . . , 11-2-q 1, 11-2-q 2,and 11-2-q 3.

In FIG. 27 , the ports 11-1-1, 11-1-2, 11-1-3, . . . of the optical SW1010-n (where n is an integer of 1 or more and N or less) are connectedto the ONUs #n1, #n2, #n3, . . . , and the ports 11-2-1, 11-2-2, 11-2-3,. . . are connected to the transmission lines 50-2 of the uplink #n1,the uplink #n2, the uplink #n3, . . . . All the other optical SWs 1010-nare connected to the ports 11-1 of the optical SW 1010-j (where j #n,and j is an integer of 1 or more and N or less) via some of the ports11-2. For example, the port 11-2-q 1 of the optical SW 1010-1 isconnected to the port 11-1-p 1 of the optical SW 1010-2, the port 11-2-q2 of the optical SW 1010-1 is connected to the port 11-1-p 1 of theoptical SW 1010-3, and the port 11-2-q 3 of the optical SW 1010-1 isconnected to the port 11-1-p 1 of the optical SW 1010-4. The port 11-2-q1 of the optical SW 1010-2 is connected to the port 11-1-p 1 of theoptical SW 1010-1, the port 11-2-q 2 of the optical SW 1010-2 isconnected to the port 11-1-p 2 of the optical SW 1010-3, and the port11-2-q 3 of the optical SW 1010-2 is connected to the port 11-1-p 2 ofthe optical SW 1010-4. The optical SW 1010-n may be connected to theports 11-1 of some optical SWs 1010-j among all the other optical SWs1010-j (where j #n, and j is an integer 1 or more and N or less) viasome of the ports 11-2.

For example, in a case where the ONU #11 transmits an uplink opticalsignal having the wavelength λ₁ addressed to the uplink #41, the opticalSW 1010-1 outputs the optical signal input from the port 11-1-1 from theport 11-2-q 3. The port 11-1-p 1 of the optical SW 1010-4 receives theoptical signal having the wavelength λ₁ output from the port 11-2-q 3 ofthe optical SW 1010-1, and outputs the optical signal from the port11-2-1.

In a case where the ONU #12 transmits an uplink optical signal havingthe wavelength λ₂ addressed to the ONU #31, the optical SW 1010-1outputs the optical signal input from the port 11-1-2 from the port11-2-q 2. The port 11-1-p 1 of the optical SW 1010-3 receives theoptical signal output from the port 11-2-q 2 of the optical SW 1010-1.The optical SW 1010-3 performs return communication similar to theoptical SW 10 b illustrated in FIG. 3 on the optical signal having thewavelength λ₂ input from the port 11-1-p 1, and outputs the opticalsignal from the port 11-1-1.

In FIG. 27 , only the uplink optical signal is illustrated. In a case ofperforming vertical bidirectional communication, a WDM filter(separation unit) that separates and transmits an uplink optical signaland a downlink optical signal is provided in the transmission lines50-1, 50-2, and 50-3. For the downlink optical signal, connection isperformed in a direction opposite to that of the above-described uplinkoptical signal.

FIG. 28 is a diagram illustrating another example of the optical SWscalability according to a cascade configuration. The configurationillustrated in FIG. 28 is different from the configuration illustratedin FIG. 27 in that the optical SW 1010-n (where n is an integer of 1 ormore and N or less) is connected to the ports 11-1 of any other opticalSW 1010-(n+1) via some ports 11-2. The optical SW 1010-(N+1) is assumedto be the optical SW 1010-1. Consequently, the plurality of optical SWs1010 are connected in series.

In FIG. 28 , the ports 11-1-1, 11-1-2, 11-1-3, . . . of the optical SW1010-n (where n is an integer 1 or more and N or less) are connected tothe ONUs #n1, #n2, #n3, . . . , and the ports 11-2-1, 11-2-2, 11-2-3, .. . are connected to the transmission lines 50-2 of the uplink #n1, theuplink #n2, the uplink #n3, . . . . The port 11-2-q 1 of the optical SW1010-n is connected to the port 11-1-p 1 of the optical SW 1010-(n+1),the port 11-2-q 2 of the optical SW 1010-n is connected to the port11-1-p 2 of the optical SW 1010-(n+1), and the port 11-2-q 3 of theoptical SW 1010-n is connected to the port 11-1-p 3 of the optical SW1010-(n+1).

For example, in a case where the ONU #11 transmits an uplink opticalsignal having the wavelength λ₁ addressed to the uplink #41, the opticalSW 1010-1 outputs the optical signal input from the port 11-1-1 from theport 11-2-q 1. The port 11-1-p 1 of the optical SW 1010-2 receives theoptical signal output from the port 11-2-q 1 of the optical SW 1010-1,and outputs the optical signal from the port 11-2-q 1 according to thewavelength λ₁. The port 11-1-p 1 of the optical SW 1010-3 receives theoptical signal output from the port 11-2-q 1 of the optical SW 1010-2,and outputs the optical signal from the port 11-2-q 1 according to thewavelength λ₁. The port 11-1-p 1 of the optical SW 1010-4 receives theoptical signal output from the port 11-2-q 1 of the optical SW 1010-3,and outputs the optical signal from the port 11-2-1 according to thewavelength λ₁.

In a case where the ONU #12 transmits an uplink optical signal havingthe wavelength λ₂ addressed to the ONU #31, the optical SW 1010-1outputs the optical signal input from the port 11-1-2 from the port11-2-q 2. The port 11-1-p 2 of the optical SW 1010-2 receives theoptical signal output from the port 11-2-q 2 of the optical SW 1010-1.The optical SW 1010-2 outputs the optical signal input from the port11-1-p 2 from the port 11-2-q 2 according to the wavelength λ₂. The port11-1-p 2 of the optical SW 1010-3 receives the optical signal outputfrom the port 11-2-q 2 of the optical SW 1010-2. The optical SW 1010-3performs return communication similar to the optical SW 10 b illustratedin FIG. 3 on the optical signal input from the port 11-1-p 2 accordingto the wavelength λ₂, and outputs the optical signal from the port11-1-1.

In FIG. 28 , only the uplink optical signal is illustrated. In a case ofperforming vertical bidirectional communication, a WDM filter thatseparates and transmits an uplink optical signal and a downlink opticalsignal is provided in the transmission lines 50-1, 50-2, and 50-3. Forthe downlink optical signal, connection is performed in a directionopposite to that of the above-described uplink optical signal.

Next, a configuration of an optical transceiver will be described withreference to FIGS. 29 to 32 . Although a part of a configuration exampleof the subscriber device 40 connected to the optical SW will bedescribed, the configuration example may be used in a control unit, amonitoring unit, or the like, and will be described as a set oftransmission and reception, but only transmission or only reception maybe used depending on a use form thereof. FIGS. 29 and 30 areconfiguration diagrams of the double-core subscriber device 401. InFIGS. 29 to 32 , in order to describe a plurality of configurations, thesame constituents are denoted by the same reference numerals, anddescription thereof may be omitted.

A subscriber device 401 illustrated in FIG. 29(A) includes an opticaltransceiver 411. The optical transceiver 411 includes a wavelengthtunable light source 451 and a variable wavelength receiver 452. Thewavelength tunable light source 451 is an example of an opticaltransmission unit, and the variable wavelength receiver 452 is anexample of an optical reception unit.

The wavelength tunable light source 451 outputs light having a setwavelength. A wavelength set to the wavelength tunable light source 451is variable. The wavelength tunable light source 451 includes, forexample, a variable wavelength laser diode (LD). The wavelength tunablelight source 451 includes, for example, any one of a combination of again medium and a resonator with a variable resonator length, forexample, a combination of a gain medium and a wavelength-selectivemedium, for example, a combination of a gain medium, a resonator with avariable resonator length, and a wavelength-selective medium. Forexample, the wavelength tunable light source 451 includes amultiplexer/demultiplexer or a power splitter and an optical transmitter(Tx) for each wavelength, and transmits an optical signal from theoptical transmitter having a set wavelength. Themultiplexer/demultiplexer is, for example, an AWG. Themultiplexer/demultiplexer or the power splitter multiplexes input lightand outputs an optical signal having the wavelength. For example, themultiplexer/demultiplexer or the power splitter has a multi-wavelengthlight source or a broadband light source, and a variable wavelengthfilter (tf) that selects and outputs a set wavelength. The variablewavelength filter causes an optical signal having a set wavelength(variable) to pass therethrough among input optical signals. Thewavelength tunable light source 451 may output a main signal (or asignal obtained by superimposing a control signal on the main signal)according to, for example, a direct modulation method. Alternatively,the wavelength tunable light source 451 further includes an externalmodulator, and may output a main signal (or a signal obtained bysuperimposing a control signal on the main signal) by using the externalmodulator. As the external modulator, a Mach-Zender (MZ), anelectro-absorption (EA), a semiconductor optical amplifier (SOA), or thelike may be used. The external modulator may have a structure integratedwith a light source. A main signal and a control signal may be modulatedby the same modulator. A main signal and a control signal may beseparately modulated by different modulators.

The variable wavelength receiver 452 includes a variable wavelengthfilter and an optical receiver. The variable wavelength filter causeslight having a set wavelength (variable) to pass therethrough amonginput optical signals. The optical receiver receives the optical signalthat has passed through the variable wavelength filter. Variablewavelength filtering, that is, selection of a signal having apredetermined wavelength may be performed after light reception. Forexample, a beat signal centered on a frequency corresponding to awavelength difference from local light having a predetermined wavelengthmay be selected with a frequency width corresponding to the band of thesignal. Depending on a configuration of the optical SW, a multiplexingmethod, or the like, a configuration using a transmitter that does nothave a variable wavelength or a configuration not using a variablewavelength filter or a multiplexer/demultiplexer may be employed.

A subscriber device 401 a illustrated in FIG. 29(B) includes an opticaltransceiver 411 a. The optical transceiver 411 a includes a wavelengthtunable light source 451, a wavelength tunable filter 453, and anoptical receiver 454. The wavelength tunable light source 451 is anexample of an optical transmission unit, and the wavelength tunablefilter 453 and the optical receiver 454 are an example of an opticalreception unit. The wavelength tunable filter 453 receives an opticalsignal from a transmission line and causes light having a set wavelengthto pass to the optical receiver 454. A wavelength set to the wavelengthtunable filter 453 is variable. The optical receiver 454 receives theoptical signal that has passed through the wavelength tunable filter453. The subscriber device 40 on the reception side may have aconfiguration not using the wavelength tunable filter 453 depending on aconfiguration of the optical SW, a multiplexing method, or the like.

A subscriber device 401 b illustrated in FIG. 29(C) includes an opticaltransceiver 411 b. The optical transceiver 411 b includes a light source455, a wavelength tunable filter 456, and a variable wavelength receiver452. The light source 455 and the wavelength tunable filter 456 are anexample of an optical transmission unit, and the variable wavelengthreceiver 452 is an example of an optical reception unit. The lightsource 455 outputs light having a single wavelength (for example, thewavelength λ₁). That is, the light source 455 does not output lighthaving a variable wavelength. The wavelength tunable filter 456 receivesan optical signal output from light source 455, and outputs an opticalsignal having a set wavelength to a transmission line. A wavelength setto the wavelength tunable filter 456 is the wavelength of the opticalsignal output from the light source 455.

A subscriber device 401 c illustrated in FIG. 30(A) includes an opticaltransceiver 411 c. The optical transceiver 411 c includes a wavelengthtunable light source 451, a plurality of optical receivers 454-1 to454-3, and a demultiplexer 457. The wavelength tunable light source 451is an example of an optical transmission unit, and the optical receivers454-1 to 454-3 and the demultiplexer 457 are an example of an opticalreception unit. FIG. 30(A) illustrates a case where there are threeoptical receivers 454-1 to 454-3, but the number of optical receivers454-1 to 454-3 is not limited. Also in the following description, thenumber of the optical receivers 454-1 to 454-3 is not particularlylimited. The demultiplexer 457 demultiplexes an optical signal inputfrom the transmission line according to wavelengths. The optical signalsdemultiplexed by the demultiplexer 457 are input to the opticalreceivers 454-1 to 454-3. The optical receivers 454-1 to 454-3 receivethe optical signals demultiplexed by the demultiplexer 457.

A subscriber device 401 d illustrated in FIG. 30(B) includes an opticaltransceiver 411 d. The optical transceiver 411 d includes a plurality oflight sources 455-1 to 455-3, a multiplexer 458, and a variablewavelength receiver 452. The light sources 455-1 to 455-3 and themultiplexer 458 are an example of an optical transmission unit, and thevariable wavelength receiver 452 is an example of an optical receptionunit. FIG. 30(B) illustrates a case where there are three light sources455-1 to 455-3, but the number of light sources 455-1 to 455-3 is notlimited. Also in the following description, the number of light sources455 is not particularly limited. The light sources 455-1 to 455-3respectively transmit optical signals having different wavelengths. Themultiplexer 458 multiplexes the plurality of optical signals output fromthe light sources 455-1 to 455-3 and outputs the multiplexed opticalsignal to a transmission line.

A subscriber device 401 e illustrated in FIG. 30(C) includes an opticaltransceiver 411 e. The optical transceiver 411 e includes a plurality oflight sources 455-1 to 455-3, a multiplexer 458, a plurality of opticalreceivers 454-1 to 454-3, and a demultiplexer 457. The light sources455-1 to 455-3 and the multiplexer 458 are an example of an opticaltransmission unit, and the optical receivers 454-1 to 454-3 and thedemultiplexer 457 are an example of an optical reception unit. In thesubscriber device 401 e, optical signals output from the light sources455-1 to 455-3 are multiplexed by the multiplexer 458 and output to atransmission line. In the subscriber device 401 e, an optical signalinput from the transmission line is demultiplexed according towavelengths in the demultiplexer 457, and the demultiplexed opticalsignals are received by the optical receivers 454-1 to 454-3.

It is desirable to combine a plurality of multiplexers/demultiplexers orcombining/branching devices if wavelengths to bemultiplexed/demultiplexed after combination are equal. That is, thedemultiplexer 457 and the multiplexer 458 may be combined.

FIGS. 31 and 32 are configuration diagrams of a single-core subscriberdevice 402. The subscriber device 402 illustrated in FIG. 31(A) includesan optical transceiver 412. The optical transceiver 412 includes awavelength tunable light source 451, a variable wavelength receiver 452,and a WDM filter 459. The optical transceiver 412 illustrated in FIG.31(A) is different from the optical transceiver 411 illustrated in FIG.29(A) in that the WDM filter 459 is further provided. The WDM filter 459separates an uplink signal and a downlink signal according towavelengths. The WDM filter 459 outputs an optical signal generated bythe wavelength tunable light source 451 to the transmission line, andoutputs an optical signal input from the transmission line to thevariable wavelength receiver 452. In the same manner as the subscriberdevice 401, the subscriber device 402 further includes an externalmodulator, and may output a main signal (or a signal obtained bysuperimposing a control signal on the main signal) by using the externalmodulator.

Here, the WDM filter 459 illustrated in FIGS. 31 and 32 may be a powersplitter. The WDM filter 459 is suitable in a case where the insertionloss is sufficiently low with respect to the power splitter andwavelengths used on the transmission side and the reception side do notoverlap. In a case where wavelengths used on the transmission side andthe reception side overlap each other, the WDM filter 459 is suitable,for example, in a case of return communication or the like between thesame type of subscriber devices.

In FIGS. 31 and 32 , the WDM filter 459 is incorporated in the opticaltransceiver 412, but may be provided outside the optical transceiver 412or outside the subscriber device 40.

A subscriber device 402 a illustrated in FIG. 31(B) includes an opticaltransceiver 412 a. The optical transceiver 412 a includes a wavelengthtunable light source 451, a wavelength tunable filter 453, an opticalreceiver 454, and a WDM filter 459 a. The optical transceiver 412 aillustrated in FIG. 31(B) is different from the optical transceiver 411a illustrated in FIG. 29(B) in that the WDM filter 459 a is furtherprovided. The WDM filter 459 a separates an uplink signal and a downlinksignal according to wavelengths. The WDM filter 459 a outputs an opticalsignal generated by the wavelength tunable light source 451 to thetransmission line, and outputs an optical signal input from thetransmission line to the wavelength tunable filter 453. The subscriberdevice 402 on the reception side may have a configuration not using thewavelength tunable filter 453 depending on a configuration of theoptical SW, a multiplexing method, or the like.

A subscriber device 402 b illustrated in FIG. 31(C) includes an opticaltransceiver 412 b. The optical transceiver 412 b includes a light source455, a wavelength tunable filter 456, a variable wavelength receiver452, and a WDM filter 459 b. The optical transceiver 412 b illustratedin FIG. 31(C) is different from the optical transceiver 411 billustrated in FIG. 29(C) in that the WDM filter 459 b is furtherprovided. The WDM filter 459 b separates an uplink signal and a downlinksignal according to wavelengths. The WDM filter 459 b outputs an opticalsignal that has passed through the wavelength tunable filter 456 to thetransmission line, and outputs an optical signal input from thetransmission line to the variable wavelength receiver 452.

A subscriber device 402 c illustrated in FIG. 32(A) includes an opticaltransceiver 412 c. The optical transceiver 412 c includes a wavelengthtunable light source 451, a plurality of optical receivers 454-1 to454-3, a demultiplexer 457, and a WDM filter 459 c. The opticaltransceiver 412 c illustrated in FIG. 32(A) is different from theoptical transceiver 411 c illustrated in FIG. 30 (A) in that the WDMfilter 459 c is further provided. The WDM filter 459 c separates anuplink signal and a downlink signal according to wavelengths. The WDMfilter 459 c outputs an optical signal generated by the wavelengthtunable light source 451 to the transmission line, and outputs anoptical signal input from the transmission line to the demultiplexer457.

A subscriber device 402 d illustrated in FIG. 32(B) includes an opticaltransceiver 412 d. The optical transceiver 412 d includes a plurality oflight sources 455-1 to 455-3, a multiplexer 458, a variable wavelengthreceiver 452, and a WDM filter 459 d. The optical transceiver 412 dillustrated in FIG. 32(B) is different from the optical transceiver 411d illustrated in FIG. 30(B) in that the WDM filter 459 d is furtherprovided. The WDM filter 459 d separates an uplink signal and a downlinksignal according to wavelengths. The WDM filter 459 d outputs an opticalsignal multiplexed by the multiplexer 458 to the transmission line, andoutputs an optical signal input from the transmission line to thevariable wavelength receiver 452.

A subscriber device 402 e illustrated in FIG. 32(C) includes an opticaltransceiver 412 e. The optical transceiver 412 e includes a plurality oflight sources 455-1 to 455-3, a multiplexer 458, a plurality of opticalreceivers 454-1 to 454-3, a demultiplexer 457, and a WDM filter 459 e.The optical transceiver 412 e illustrated in FIG. 32(C) is differentfrom the optical transceiver 411 e illustrated in FIG. 30(C) in that theWDM filter 459 e is further provided. The WDM filter 459 e separates anuplink signal and a downlink signal according to wavelengths. The WDMfilter 459 e outputs an optical signal multiplexed by the multiplexer458 to the transmission line, and outputs an optical signal input fromthe transmission line to the demultiplexer 457.

It is desirable to combine a plurality of multiplexers/demultiplexers orcombining/branching devices if wavelengths to bemultiplexed/demultiplexed after combination are equal. That is, thedemultiplexer 457 and the multiplexer 458, the multiplexer 458 and theWDM filter 459 e, the demultiplexer 457 and the WDM filter 459 e, andthe demultiplexer 457, the multiplexer 458, and the WDM filter 459 e maybe combined.

The configurations of the single-core subscriber device 401 and thedouble-core subscriber device 402 have been described above. In thepresent invention, any of the configurations illustrated in FIGS. 29 to32 may be used as the subscriber device 40.

Next, configuration examples of the monitoring unit 60 and themonitoring unit 65 will be described. First, in the above description, asignal is branched and monitored by using a power splitter, but a mediumin which a gain, an applied voltage, a current, or a resistance changesdue to conduction of the signal at a frequency of at least a carrierwave of an AMCC, for example, a semiconductor amplifier may beincorporated in a transmission line without branching. Awavelength-multiplexed signal may also be monitored without branching byusing a medium having high wavelength dependency on changes in gain,voltage, current, resistance, and the like by using a superlatticestructure such as multiple quantum well (MQW) or a photonic crystal.

Hereinafter, configuration examples of the monitoring unit 60 and themonitoring unit 65 will be described with reference to FIGS. 33 to 37 inthe case of branching. In FIGS. 33 to 37 , the monitoring unit 60 willbe described as an example. Although FIGS. 33 to 37 illustrate anexample of monitoring directions such as an uplink direction and adownlink direction, the monitoring unit 60 may monitor only onedirection related to output from the subscriber device 40, for example,from the viewpoint of monitoring the subscriber device 40. In the caseof an example of only one direction, both directions are obtained byreplacing the transmitter and the receiver with a combination of atransmitter and a receiver connected to, for example, a transceiver, apower splitter, or a multiplexer/demultiplexer.

Although the receiver and the transmitter are described in proximity tothe power splitter 61, the multiplexer/demultiplexer, and the likebranching from a transmission line, the receiver and the transmitter maybe disposed far away, for example, via one or a plurality of opticalSWs, and the receiver and the transmitter of the control unit may beconnected to the receiver and the transmitter of the monitoring unit 60by assuming that the receiver and the transmitter of the control unitalso serve as the receiver and the transmitter thereof.

The monitoring unit 60 monitors an optical signal. At the time ofmonitoring, the optical receiver or the optical transceiver is disposedin the vicinity of a combining/branching device or amultiplexer/demultiplexer or at a location where an optical signal canbe connected. The monitoring unit 60 branches an optical signal with acombining/branching device or a multiplexer/demultiplexer, performsmonitoring by using the received optical signal, and further receives acontrol signal superimposed on the received optical signal.

The monitoring unit 60 includes a combining/branching device or amultiplexer/demultiplexer provided at a port on an input side, a passingside, or an output side of an optical SW, a transmission line, or aconnection point thereof, and a blocking unit that blocks a main signalin some cases. For example, a multiplexer/demultiplexer may be disposedat the port 11-2 at the ground side, the transmission line 2, or aconnection point thereof, and separate an input optical signal,according to wavelengths, into an uplink optical signal from the opticalSW and a downlink optical signal input from another ground or a highernetwork and output the optical signals to the optical SW. The blockingunit in the case of including the blocking unit is preferably disposedat a location in a multiplexed or merged state, for example, in a casewhere the disposition is set or changed in both uplink and downlinkdirections, and is preferably disposed at a location in a demultiplexedor branched state, for example, in a case where the disposition isseparately set or changed in uplink and downlink directions.

The monitoring unit 60 may be connected via an optical SW different fromthe optical SW connected to the subscriber device 40 that is a controltarget. For example, an optical signal separated from a transmissionline through which the combining/branching device transmits the opticalsignal of the subscriber device 40 that is a control target is input tothe optical SW connected to the monitoring unit 60 separately from theconnection of the subscriber device 40, multiplexed as necessary,transmitted to the optical SW connected to the monitoring unit 60, andinput to the monitoring unit 60. Alternatively, the optical signal isnot input to the optical SW, but is directly input to an optical SWconnected to the control unit or the monitoring unit 60.

The ports configuring the optical SW may be divided into a plurality ofgroups, and the combining/branching device or themultiplexer/demultiplexer may be provided in the port 11-2 belonging toone group in a case where the ports are not connected in the group, thetransmission line 2 connected thereto, or the transmission line 2connected to the port 2. The branching may be performed before or afterwavelength separation. The combining/branching device or themultiplexer/demultiplexer may be provided closer to the optical SW sidethan a multiplexer/demultiplexer for uplink and downlink multiplexing,or may be provided closer to the transmission line side. In a case wherethe combining/branching device or the multiplexer/demultiplexer isprovided closer to the transmission line side, uplink and downlinkoptical signals transmitted through the transmission line can bebranched by one device. In this case, the branched uplink optical signaland downlink optical signal are respectively input to ports of theoptical SW. The optical SW outputs the input optical signals from portsconnected to the monitoring unit 60. Consequently, the monitoring unit60 receives the branched optical signals.

A monitoring unit 60 a illustrated in FIG. 33(A) shows a specificconfiguration of the monitoring unit 60. The monitoring unit 60 aincludes a power splitter 61 and a plurality of receivers 62-1 and 62-2.The receivers 62-1 and 62-2 receive optical signals branched by thepower splitter 61. The number of receivers 62-1 and 62-2 correspondingto the number of branches of the power splitter 61 may be provided. FIG.33(A) illustrates an example in which a 2×2 power splitters 61 is used,and a total of one power splitter is provided, that is, the number ofpower splitters is obtained by subtracting one that is the number ofpaths of a main signal from two that is the number of branches branchedin each direction or other than the path of the main signal on the inputside and the output side. In a case of a 3×3 power splitter 61, twopower splitters may be provided. From the viewpoint of reducing theinfluence of reflection and the like, the power splitter 61 of 1×2, 1×3,or the like that does not include ports not to be monitored may be used.In this case, the receiver 62-1 or 62-2 may set the following: thenumber of branches (2)−the number of main signal path (1)=1 and thenumber of branches (1)−the number of main signal path (1)=0; the numberof branches (3)−the number of main signal path (1)=2, and the number ofbranches (1)−the number of main signal path (1)=0.

A path other than the main signal branched by the power splitter 61 maybe branched as in the WDM device 63 b of FIG. 33(B) and the main signalmay be received, or a plurality of power splitters 61 may be provided inthe main signal path and may be branched and the main signal may bereceived.

A monitoring unit 60 a illustrated in FIG. 33(A) shows a specificconfiguration of the monitoring unit 60. The monitoring unit 60 aincludes a power splitter 61 and a plurality of receivers 62-1 and 62-2.The receivers 62-1 and 62-2 receive optical signals branched by thepower splitter 61. The number of the receivers 62 is not particularlylimited.

A monitoring unit 60 b illustrated in FIG. 33(B) shows a specificconfiguration of the monitoring unit 65. The monitoring unit 60 bincludes a power splitter 61, a plurality of receivers 62-1 to 62-6, anda plurality of WDM devices 63 b-1 and 63 b-2. The receivers 62-1 to 62-3are connected to the WDM device 63 b-1. The receivers 62-4 to 62-6 areconnected to the WDM device 63 b-2. The WDM device 63 b-1 demultiplexesan optical signal branched by the power splitter 61 and outputs thedemultiplexed optical signals to the receivers 62-1 to 62-3. The WDMdevice 63 b-2 demultiplexes an optical signal branched by the powersplitter 61 and outputs the demultiplexed optical signals to thereceivers 62-4 to 62-6. The number of the WDM devices 63 b is notparticularly limited.

The monitoring unit 60 c illustrated in FIG. 33(C) includes a powersplitter 61, a plurality of receivers 62-1 and 62-2, and a WDM device 63c. The WDM device 63 c multiplexes a plurality of input optical signalsand outputs the multiplexed optical signal to a transmission line 601.The WDM device 63 c demultiplexes an optical signal input from thetransmission line 601 and outputs the demultiplexed optical signals totransmission lines 602-1 and 602-2.

A monitoring unit 60 d illustrated in FIG. 34(A) includes a plurality ofpower splitters 61-1 to 61-3, a plurality of receivers 62-1 to 62-6, anda WDM device 63 d. The power splitter 61-1 is provided in a transmissionline 602-1, the power splitter 61-2 is provided in a transmission line602-2, and the power splitter 61-3 is provided in a transmission line602-3. The receivers 62-1 and 62-2 are connected to the power splitter61-1, the receivers 62-3 and 62-4 are connected to the power splitter61-2, and the receivers 62-5 and 62-6 are connected to the powersplitter 61-3. The WDM device 63 d demultiplexes an optical signal inputfrom the transmission line 601 and outputs the demultiplexed opticalsignals to the transmission lines 602-1 to 602-3. The WDM device 63 dmultiplexes optical signals input from the transmission lines 602-1 to602-3 and outputs the multiplexed optical signal to the transmissionline 601.

In FIG. 34(A), the receivers 62-1 to 62-6 are provided in the respectivetransmission lines 602-1 to 602-3 after demultiplexing by the WDM device63 d when viewed from the transmission line 601 or before multiplexingby the WDM device 63 d when viewed from the transmission line 602, butthe receiver 62 does not have to be provided in a transmission line forwhich reception is not required.

A monitoring unit 60 e illustrated in FIG. 34(B) includes a plurality ofpower splitters 61-1 and 61-2, a plurality of receivers 62-1 and 62-2,and a plurality of WDM devices 63 e-1 and 63 e-2. Transmission lines602-1 and 602-2 are provided between the WDM device 63 e-1 and the WDMdevice 63 e-2. The power splitter 61-1 is provided in the transmissionline 602-1, and the power splitter 61-2 is provided in the transmissionline 602-2. The receiver 62-1 is connected to the power splitter 61-1,and the receiver 62-2 is connected to the power splitter 61-2. The WDMdevice 63 e-1 demultiplexes an optical signal input from thetransmission line 601 and outputs the demultiplexed optical signals tothe transmission lines 602-1 and 602-2. The WDM device 63 e-1multiplexes optical signals input from the transmission lines 602-1 and602-2 and outputs the multiplexed optical signal to the transmissionline 601. The WDM device 63 e-2 demultiplexes an optical signal inputfrom the transmission line 603 and outputs the demultiplexed opticalsignals to the transmission lines 602-1 and 602-2. The WDM device 63 e-2multiplexes optical signals input from the transmission lines 602-1 to602-2 and outputs the multiplexed optical signal to the transmissionline 603.

In FIG. 34(B), the receivers 62-1 and 62-2 are provided in thetransmission lines 602-1 and 602-2 after demultiplexing and beforemultiplexing, but the receiver 62 does not have to be provided in atransmission line for which reception is not required.

The monitoring unit may control the subscriber device 40. In a casewhere a control signal is exchanged with the subscriber device 40, themonitoring unit may set or change a wavelength of the subscriber device40 similarly to the control unit 20. However, in a case where thesetting, particularly the wavelength is changed, an optical signal otherthan the wavelength set at the time of the change does not reach anunintended destination. Therefore, it is desirable to set a wavelengthsuch that an output from a target device does not reach a destinationuntil the change is completed.

A configuration in which the monitoring unit performs control will bedescribed with reference to FIG. 35 .

A monitoring unit 60 f illustrated in FIG. 35(A) includes a powersplitter 61, a plurality of receivers 62-1 and 62-2, and a modulator 64.The power splitter 61 and the modulator 64 are provided in atransmission line 601. As described above, in the monitoring unit 60 f,the modulator is provided in the middle of the path of the main signal,and the main signal is modulated by the modulator 64. As the modulator,modulation may be performed by an amplifier that modulates anamplification factor according to an external modulator or a controlsignal, or due to gain saturation according to an optical signal fromthe monitoring unit 60 f, intermodulation, or non-linear effects such asfour-wave mixing and the Raman effect.

As long as an extinction ratio of the modulator is high enough not toaffect other optical signals, the modulator may also serve as a blockingunit.

Although FIG. 35(A) illustrates the configuration in which themonitoring unit 60 f includes the power splitter 61, the receivers 62-1to 62-2, and the modulator 64, the modulator 64 may be replaced with adevice capable of modulating an input intensity monitor and an output ata frequency of about a carrier wave of the AMCC, for example, amulti-electrode optical semiconductor amplifier.

In a case of modulation with external light, the power splitter 61 alsoserves as a modulator without separately providing the modulator 64. Thepower splitter 61 includes a semiconductor optical amplifier, a highlynon-linear fiber (HNLF), a non-linear optical crystal, a periodicallypoled optical element (for example, periodically poled potassium titanylphosphate (PPKTP), periodically poled lithium niobate (PPLN), andperiodically poled lithium tantalate (PPLT)) that facilitatesquasi-phase matching for non-linearity, and the like, which have largegain saturation and a large non-linear effect, and causes a signal andexternal light to act.

In a case where a signal that has already been modulated with the AMCCis re-modulated, the influence of the pre-modulation is assumed. In sucha case, a frequency band of the control signal is desirably differentfrom a frequency band at the pre-modulation. For example, in a casewhere a modulation band of a signal is B to such an extent that themodulation sidebands of pre-modulation and of new modulation do notoverlap each other, a difference between the frequency bands may be setto 2 B or more, or may be set to 2 B or more from the viewpoint ofpreventing interference, or may be conversely set to about 0.5 times to0.8 times thereof on the assumption that the signal is cut out by afilter. The modulation may be performed by another modulator 64 afterthe inverse modulation illustrated in FIG. 35(B). In this case, sincethe influence of the pre-modulation is reduced, the frequency bands maybe allowed to overlap. Modulation may be performed with a signalcorresponding to a product of inverse modulation of pre-modulation andnew modulation, and modulation in a plurality of modulators 64 may beperformed by modulation of one modulator 64. The monitoring unit 60 fmay perform a process described with reference to FIG. 35(B) in order toreduce the influence of the AMCC on the main signal.

As illustrated in FIG. 35(B), the monitoring unit 60 f may modulate themain signal modulated with an AMCC according to the same modulationmethod as that of the AMCC received by the receiver 62-2 and a reversesignal (in a case of I/O intensity modulation, 0 is superimposed on asignal modulated with 1, 1 is superimposed on a signal modulated with 0,and the modulation gives an opposite phase and an intensity that exactlycancels the signal). Consequently, the influence on a main signal of theAMCC can be reduced.

A monitoring unit 60 g illustrated in FIG. 36 includes a plurality ofpower splitters 61-1 and 61-2, a plurality of receivers 62-1 and 62-2, aplurality of WDM devices 63 g-1 to 63 g-2, and a plurality of modulators64 g-1 to 64 g-2. Transmission lines 602-1 and 602-2 are providedbetween the WDM device 63 g-1 and the WDM device 63 g-2. The modulator64 g-1 and the power splitter 61-1 are provided in the transmission line602-1, and 64 g-2 and the power splitter 61-2 are provided in thetransmission line 602-2. The receiver 62-1 is connected to the powersplitter 61-1, and the receiver 62-2 is connected to the power splitter61-2. The WDM device 63 g-1 demultiplexes an optical signal input fromthe transmission line 601 and outputs the demultiplexed optical signalsto the transmission lines 602-1 and 602-2. The WDM device 63 g-1multiplexes optical signals input from the transmission lines 602-1 to602-2 and outputs the multiplexed optical signal to the transmissionline 601. The WDM device 63 e-2 demultiplexes an optical signal inputfrom the transmission line 603 and outputs the demultiplexed opticalsignals to the transmission lines 602-1 and 602-2. The WDM device 63 e-2multiplexes optical signals input from the transmission lines 602-1 to602-2 and outputs the multiplexed optical signal to the transmissionline 603. Optical signals input from the transmission lines 602-1 and602-2 to the WDM device 63 e-1 and the WDM device 63 e-2 are modulatedby the modulators 64 g-1 and 64 g-2.

In FIG. 36 , branched optical signals are modulated after being receivedby the receivers 62-1 and 62-2. However, in a case where it is notnecessary to consider quality of a received optical signal due tomodulation, for example, deterioration in a signal-to-noise ratio (SN)of a received control signal or the like, a modulated optical signal maybe branched by the power splitters 61-1 and 61-2 and received by thereceivers 62-1 and 62-2.

A configuration in which the monitoring unit uses a transmitter will bedescribed. Similarly to the subscriber device 40 or the control unit 20,the monitoring unit includes an optical transceiver and a variablewavelength or non-variable wavelength optical transceiver, and isconnected to a port of an optical SW. If the transmitter is a variablewavelength transmitter, an optical signal having any wavelength can betransmitted. The monitoring unit transmits a control signal to thesubscriber device 40 by using an optical signal. A power splitter of atransmission line for transmitting an optical signal of the subscriberdevice 40 that is a control target merges a control signal with theoptical signal transmitted through the transmission line. With thisconfiguration, even in a state in which the subscriber device 40 isperforming normal communication, the monitoring unit can receive aconnection destination change request or the like from the subscriberdevice 40, transmit a control signal, and perform wavelength switchingor the like for the subscriber device 40. A specific configuration inwhich the monitoring unit includes a transmitter will be describedlater.

In a case where the subscriber device 40 is performing normalcommunication, communication with the control unit 20 in a case wherethe control unit 20 controls the subscriber device 40 by using anoptical signal directly or via an optical SW or the like cannot beperformed. Since the monitoring unit includes the transmitter, it ispossible to give instructions for various settings or the like of thesubscriber device 40. That is, the monitoring unit receives an opticalsignal inserted and separated into a transmission line through which theoptical signal is transmitted to the subscriber device 40 that is acontrol target with the power splitter.

An example will be described using an AMCC. Typically, in the AMCC, amain signal and an AMCC signal are modulated with a signal obtained bysuperimposing the main signal and the AMCC signal at an electricalstage, or the main signal is further modulated at an optical stage. Incontrast, the transmitter of the monitoring unit inputs and multiplexesan optical signal corresponding to the control signal separately fromthe main signal. A wavelength of the optical signal corresponding to thecontrol signal is a wavelength that passes through the same path as thatof the main signal from the transmitter to a location where at least acontrol signal corresponding to the AMCC is received. The monitoringunit does not modulate the main signal but performs intensity modulationor the like on the separately input optical signal intensity at afrequency of a carrier wave of the AMCC, and thus an optical signalobtained by combining the main signal and the control signalcorresponding to the AMCC is equivalent to that modulated at thefrequency of the carrier wave of the AMCC.

Here, the example in which the control signal is received afterintensity modulation thereof together with the main signal has beendescribed, but in a case of phase modulation or the like, the controlsignal may be received by using delay detection or local light emission.

Here, if a wavelength difference between the main signal and the controlsignal corresponding to the AMCC is separated to such an extent thatbeat noise can be ignored, for example, by a sum of line widths of bothpieces of light, and if the line widths are equal, the wavelengthdifference is separated by twice or more the line width, demodulationcan be performed in the same manner as in the case of modulation withthe AMCC similarly to an average value of the light intensities of bothpieces of light in the time of one bit or one baud of the AMCC. In acase where a modulated sideband at the frequency of the carrier wave inthe AMCC and a modulated sideband at a bit rate or a baud rate of themain signal are superimposed, it is difficult to perform demodulationaccording to direct detection with the same modulation as usual.However, for example, coherent reception or the like may be performed,and reception may be performed after removal at an electrical stage bymaximum likelihood determination or the like, or a phase of light of theoptical signal of the control signal corresponding to the AMCC may besynchronized with a phase of light of the optical signal of the mainsignal. In a case where phase synchronization is performed, evenmodulation using a phase can be performed with the AMCC. In this case,modulation is performed such that a phase after multiplexing becomes aphase after modulation.

For example, an intensity or a wavelength of signal light and controllight may be measured by different measurement means, or may be measuredby the same measurement means such that the optical signal of the mainsignal and a part of an optical signal input from the transmitter of themonitoring unit to the power splitter can be received by the receiver ofthe monitoring unit. The latter has an effect of reducing the number ofmeasurement means. For example, the influence of beat noise betweenpieces of light on the main signal may be observed and adjusted aftermultiplexing. For example, the main signal is measured before thecontrol light is multiplexed, and then a signal after the control lightis multiplexed is equivalent to a signal to which the desired AMCC isapplied, or the influence or the like of the beat noise between piecesof light on the main signal is measured after the multiplexing. Theintensity or the wavelength of the optical signal of the control signalis adjusted. In the case of phase synchronization, feedback may beperformed in measurement after multiplexing.

Next, an example of another configuration using a transmitter in themonitoring unit will be described with reference to FIG. 37 . Instead ofbeing installed at a port of the optical SW 10, a transmission line, ora connection point thereof, as illustrated in FIG. 37 , the control unit20 may loop using a return transmission line (upper side in the figure),or may cross the optical SW 10 (lower side in the figure) similarly toan electrical processing unit that will be described later.

For example, a monitoring unit 60 h terminates the main signal, and thetransmitter transmits an optical signal obtained by superimposing theAMCC on the main signal subjected to photoelectric conversion, orfurther modulating an optical signal modulated with the main signal,with the AMCC. Unlike the monitoring unit 60 h described above, themonitoring unit 60 h does not include a power splitter that combines andbranches the main signal, but may be similarly provided at a port on aninput side, a passing side, or an output side of an optical SW, atransmission line, or a connection point thereof. In this configuration,since the signal is temporarily terminated, a wavelength to themonitoring unit 60 h and a wavelength from the monitoring unit may bedifferent as long as they are wavelengths transmitted through a desiredpath.

The monitoring unit 60 h does not have to include an optical receiver oran optical transceiver, and may transmit and output a branched opticalsignal to the control unit 20 via the optical SW 10, for example. In thecase of outputting to the control unit 20, the control unit 20 includesan optical receiver or an optical transceiver, and the monitoring unit60 h has a function of setting a path between a power splitter or amultiplexer/demultiplexer provided at a port on an input side, a passingside, or an output side of an optical SW, a transmission line, or aconnection point thereof, and the control unit 20, and setting the powersplitter, the multiplexer/demultiplexer, or the path as necessary. Thepath may be realized by the optical SW, and may also be set by thecontrol unit.

The monitoring unit 60 h may include an optical receiver or an opticaltransceiver, and may further include a blocking unit. At the time ofinitial setting, setting change, and abnormality detection, a path fromthe monitoring unit to an output destination may be blocked or blockedby the blocking unit to set, change, and block a subscriber device.

As described above, the monitoring units 60 to 60 h monitor an opticalsignal. The monitoring units 60 to 60 h performs monitoring by using anoptical signal branched by a power splitter or a WDM device, and furtherreceives a control signal superimposed on the received optical signal.Although FIGS. 33 to 37 illustrate the configuration in which themonitoring units 60 to 60 h include the receiver 62, the monitoringunits 60 to 60 h may include a transmitter.

The monitoring units 60 to 60 h may be connected via an optical SWdifferent from an optical SW connected to the subscriber device 40 thatis a control target. In this case, an optical signal separated by thepower splitter 61 in the transmission line for transmitting an opticalsignal of the subscriber device 40 that is a control target is input toan optical SW that is different from the optical SW connected to thesubscriber device 40 and is connected to the monitoring units 60 to 60h. In this case, signals are multiplexed as necessary, transmitted tothe optical SW connected to the monitoring units 60 to 60 h, andconnected to the monitoring units 60 to 60 h.

In the following description, the monitoring units 60 to 60 h will bedescribed as the monitoring unit 60 unless otherwise distinguished.

Hereinafter, an example of an optical access system using the optical SWhaving the above-described functions will be described.

(Configuration Example of Optical Access System 100)

FIG. 38 is a diagram illustrating a configuration example of an opticalaccess system 100. The optical access system 100 includes an opticalgateway (GW) 200 and an operation system (OPS) 300. The OPS 300 may beintegrated with the control unit 20, and both may be referred to as acontrol unit or an OPS as a representative. The subscriber device 40 iscommunicatively connected to a higher network such as the opticalcommunication network 30 illustrated in FIG. 1 via the optical accesssystem 100.

The subscriber device 40 is a device on an optical subscriber side. Thesubscriber device 40 is connected to the optical GW 200 via atransmission line 501. The transmission line 501 is, for example, anoptical fiber. The optical GW 200 is a device in a communicationstation. The subscriber device 40 and the optical GW 200 in a portiondenoted by the reference sign N1 are connected via, for example, thetransmission line 501 or a power splitter 502. A configuration of anetwork connected from the subscriber device 40 to the optical GW 200may be various network topologies such as a point-to-point (P-to-P)configuration, a PON configuration, a bus type, a mesh type, a ringtype, and a multi-ring type. For example, a power splitter 502 or thelike may be provided in the transmission line 501, and a plurality ofsubscriber devices 40 may be connected to one transmission line 501. Theoptical GW 200 is connected to another station, a core network, or thelike via a transmission line 511 and a transmission line 512. Thetransmission line 511 and the transmission line 512 are, for example,optical fibers. The transmission line 511 transmits an uplink signal,and the transmission line 512 transmits a downlink signal. Thetransmission line 511 and the transmission line 512 are an example of amultiplex communication transmission line for transmitting awavelength-multiplexed optical signal. The optical GW 200 to anotherstation or a core network in a portion denoted by the reference sign N2are connected via, for example, the transmission line 511 or atransmission line 512 of an optical fiber, and are connected such thatconnection between the grounds is a full mesh. In this configuration, acase where the optical GW 200 is installed in a station at the ground Aand is connected to an optical communication device set in a station atthe ground B and an optical communication device installed in a stationat the ground C via the optical communication network 30 or the likewill be described as an example. The optical communication devices atthe ground B and the ground C to which the optical GW 200 is connectedmay be the optical GW 200.

The subscriber device 40 is connected to the optical GW 200 via atransmission line 501. The subscriber device 40 includes the opticaltransceiver 41. The optical transceiver 41 is a wavelength tunableoptical transceiver. The optical transceiver 41 is, for example, anoptical transceiver that mutually converts an optical signal and anelectrical signal. The subscriber device 40 can select and set a uniquewavelength in the optical transceiver 41 according to atransmission/reception destination. The subscriber device 40 sets awavelength to be used in the optical transceiver 41 according to aninstruction received from the optical GW 200. M (where M is an integerof 1 or more) subscriber devices 40 connected to the optical GW 200 willbe referred to as subscriber devices 40-1 to 40-M.

The optical GW 200 includes an optical SW 210, a wavelengthmultiplexer/demultiplexer 220, a control unit 230, a multiplexer 241, ademultiplexer 242, a branching unit 250, and a monitoring unit 260. Themonitoring unit 260 may be replaced with any one of the monitoring units60 to 60 h described above.

The optical SW 210 has a plurality of input/output ports (hereinafter,referred to as “ports”), and connects two or more ports. The optical SW210 can freely switch an optical path between ports. A port throughwhich an uplink signal is input and output will be referred to as anuplink port, and a port through which a downlink signal is input andoutput will be referred to as a downlink port. Each port of the opticalSW 210 is connected to a transmission line.

The wavelength multiplexer/demultiplexer 220 performs verticaldemultiplexing in which an uplink signal and a downlink signal areseparated according to wavelengths. The wavelengthmultiplexer/demultiplexer 220 receives an uplink optical signaltransmitted by the subscriber device 40 from the transmission line 501and outputs the uplink optical signal to the optical SW 210 via thetransmission line 521. The wavelength multiplexer/demultiplexer 220receives a downlink optical signal output from the optical SW 210 fromthe transmission line 522 and outputs the downlink optical signal to thesubscriber device 40 via the transmission line 501.

The control unit 230 is connected to an uplink port and a downlink portto which the subscriber device 40 is not connected among the ports ofthe optical SW 210. The uplink port of the optical SW 210 is connectedto a port on the transmission side of the control unit 230 via atransmission line 531. The downlink port of the optical SW 210 isconnected to a port on the transmission side of the control unit 230 viaa transmission line 533. The control unit 230 includes a wavelengthdemultiplexer 231, an optical receiver (Rx) 232 for each wavelengthchannel, and a wavelength tunable transmitter 233. The wavelengthdemultiplexer 231 is, for example, an AWG. The wavelength demultiplexer231 demultiplexes light input to the port on the reception side via atransmission line 540 for each wavelength. The wavelength demultiplexer231 outputs the demultiplexed light to the optical receiver 232 thatreceives an optical signal having a wavelength of the light. Thewavelength tunable transmitter 233 includes a wavelength tunable laserdiode (LD) that generates light having a variable wavelength. Thewavelength tunable transmitter 233 transmits an optical signal having avariable wavelength by using light generated by the wavelength tunablelaser diode. The wavelength tunable transmitter 233 outputs an opticalsignal using the generated light from the port on the transmission sideto the transmission line 533.

The multiplexer 241 multiplexes the uplink optical signals havingdifferent wavelengths output from the plurality of transmission lines541 by the optical SW 210, and outputs the multiplexed signal to thetransmission line 511 connected to another ground. The demultiplexer 242receives an optical signal transmitted from any other ground from thetransmission line 512 and demultiplexes the received downlink opticalsignal according to wavelengths. The demultiplexer 242 inputs each ofthe demultiplexed downlink optical signals to the optical SW 210 via aplurality of transmission lines 542 connected to the uplink portcorresponding to the wavelength of the optical signal.

The branching unit 250 is provided in the transmission line 511 and thetransmission line 512. The branching unit 250 includes power splitters251 and 252. The power splitter 251 branches an uplink optical signaltransmitted through the transmission line 511, and inputs the signal tothe optical SW 210 via the transmission line 551. The power splitter 252branches a downlink optical signal transmitted through the transmissionline 512, and inputs the signal to the optical SW 210 via thetransmission line 552.

The monitoring unit 260 includes a wavelength demultiplexer 261 and anoptical receiver (Rx) 262 for each wavelength. The wavelengthdemultiplexer 261 is connected to the optical SW 210 via a transmissionline 560. The optical SW 210 outputs an optical signal input from a portconnected to the transmission line 541 or the transmission line 542 to aport connected to the transmission line 560. Consequently, thewavelength demultiplexer 261 receives the optical signal branched by thebranching unit 250. The wavelength demultiplexer 261 demultiplexes theinput optical signal for each wavelength. The wavelength demultiplexer261 outputs the demultiplexed light to the optical receiver 262 thatreceives an optical signal having the wavelength of the light. Themonitoring unit 260 monitors a state of communication performed by thesubscriber device 40 by using the optical signal received by the opticalreceiver 262. The monitoring unit 260 may output a monitoring result tothe control unit 230 or a control unit 301 included in the OPS 300.Here, the control unit 230 and the control unit 301 are used, but theymay be the same. The monitoring unit 260 may output a monitoring resultto the control unit 230, and the control unit 230 may output the outputmonitoring result to the control unit 301. The control unit 230 and thecontrol unit 301 may be the same. In that case, the output from thecontrol unit 230 to the control unit 301 does not have to be output tothe outside of the control unit.

The OPS 300 includes the control unit 301 and a management DB 350. Thecontrol unit 301 is connected to the optical GW 200. The control unit301 includes a wavelength controller 310 and an optical SW controller320. The wavelength controller 310 stores information indicating awavelength of light used by each user (or each service). The wavelengthcontroller 310 refers to this information and dynamically allocates awavelength to be used by each user. The wavelength controller 310 may beinstalled in a building different from that of the optical GW 200 andconnected to the optical SW 210 or the optical SW controller 320 via anetwork. The wavelength controller 310 manages and controls informationregarding which user is connected to which port of the optical SW 210and which wavelength is used in real time by sharing each piece ofconnection information. The control unit 301 may be installed for eachoptical SW 210 or may be installed for plurality of optical SWs. Asdescribed above, the wavelength controller 310 executes processingsimilar to that of the wavelength controller 25 in FIG. 2 .

The control unit 301 is connected to the management database (DB) 350.The control unit 301 exchanges information regarding a user and a usewavelength with the management DB 350. The management DB 350 stores ause wavelength of each user and destination information. The destinationis represented by, for example, the ground A or the ground B. Themanagement DB 350 manages information regarding all users connected tothe optical access system 100.

FIG. 39 is a diagram illustrating an example of a SW connection table.The SW connection table indicates a connection destination of each portof the optical SW 210. That is, a port through which an optical signalis input and output may be used as information for identifying thesubscriber device 40, the control unit 230, the branching unit 250, themonitoring unit 260, the ground, and the like of a transmission sourceor a transmission destination of the optical signal.

The wavelength table includes a user wavelength table and aninter-station wavelength table.

FIG. 40 is a diagram illustrating an example of the user wavelengthtable. The user wavelength table indicates a wavelength used fortransmission by each user, a wavelength used for reception, a freewavelength not used for transmission and reception, and a wavelengththat cannot be used due to a failure. The management DB 350 may managethe wavelength table for each transmission line connected to the opticalSW 210.

FIG. 41 is a diagram illustrating an example of the inter-stationwavelength table. The inter-station wavelength table indicates awavelength used for a certain ground to perform communication with eachof other grounds, a free wavelength not used for a certain ground toperform communication with each of other grounds, and a wavelength thatcannot be used for a certain ground to perform communication with eachof other grounds due to a failure.

Here, an operation when the new subscriber device 40 is connected willbe described. FIG. 42 is a flowchart illustrating initial settingprocess of the optical access system 100 when a new subscriber device isconnected. An operation of the optical access system 100 when the newsubscriber device 40-1 is connected to the optical GW 200 will bedescribed with reference to FIGS. 38 and 42 . It is assumed that whichport of the optical SW 210 is connected to each port of the wavelengthdemultiplexer 261 (AWG) of the control unit 230 is confirmed in advanceby the control unit 230.

First, user application is performed before connecting the newsubscriber device 40-1. For example, communication between the ground Aand the ground B can be performed by the user application. A businessoperator registers user information, initial destination information,and the like in the management DB 350 of the OPS 300 on the basis of theuser application (step S1). The user information is, for example,information for obtaining a wavelength or the like that can be used bythe optical transceiver 41. The OPS 300 refers to the SW connectiontable and allocates a port of the optical SW 210 to which the subscriberdevice 40-1 is to be connected from among free ports of the optical SW210 (step S2). Here, at least two ports such as an uplink port and adownlink port are allocated in the case of double cores, and at leastone port is allocated in the case of the single-core bidirectional type.The OPS 300 registers information indicating that the allocated port isconnected to the subscriber device 40-1 in the SW connection table. In acase where the control unit 20 controls the subscriber device 400 withan optical signal, the optical SW controller 320 of the OPS 300 controlsthe optical SW 210 such that an optical signal is transmitted andreceived between the port allocated to the target subscriber device 40-1and the port to which the control unit 230 is connected. In a case wherethe subscriber device 40 is controlled with an optical signal via theoptical SW 210 and the monitoring unit 260, the optical SW 210 isconnected via the monitoring unit 260, and in a case where thesubscriber device 40 is not controlled with an optical signal via theoptical SW 210 and via the monitoring unit 260 or the communicationunit, or in a case where the subscriber device 40 is not controlled withan optical signal, if the port to be connected is not connected by theoptical SW 210, the state may be maintained, or if the port to beconnected is blocked, the state may be maintained.

When the new subscriber device 40-1 is connected, the subscriber device40-1-performs an initialization process and transmits a connectionrequest (register request) by using an optical signal (step S3).

In a case where a propagation delay or a transmission distance ismeasured on the basis of a register request, in a case where afunctional unit that has received the request, for example, the controlunit 230, the monitoring unit 260, or the communication unit, and afunctional unit that uses a measured value, for example, a control unit,a monitoring unit, or a communication unit that is different from thefunctional unit that has received the request, a band allocating unitthat gives a transmission permission notification, an opposing device,or the like use the value, the measurement is performed again by thefunctional unit that uses the value, or the propagation delay or thetransmission distance between the functional unit that has performed themeasurement and the functional unit that uses the value is adjusted andused in consideration of wavelength dispersion, polarization dispersion,or mode dispersion.

The subscriber device 40-1 automatically performs the initializationprocess before connection or immediately after connection. Thewavelength multiplexer/demultiplexer 220 receives a connection requestfrom the transmission line 501 and outputs the connection request to theoptical SW 210 via the transmission line 521. The optical SW 210 outputsa connection request input from a port connected to the subscriberdevice 40-1 to an output port to which the control unit 230 is connectedin a case where the control unit 20 controls the subscriber device 400by an optical signal. The input to the reception port of the controlunit may be performed via the monitoring unit 260. The control unit 230receives the connection request from the reception port via thetransmission line 531. The control unit 230 analyzes the input opticalsignal, and checks whether there is a problem in an initial setwavelength or optical power (step S4).

In a case where there is a problem in a wavelength or optical power, thecontrol unit 230 transmits a restart or initialization instruction tothe subscriber device 40-1. After the restart or the initial setting,the process returns to step S3, and the subscriber device 40-1 transmitsthe connection request again.

The control unit 230 analyzes the optical signal received from thesubscriber device 40-1, and outputs a connection request to the controlunit 301 in a case where it is checked that there is no problem. Thecontrol unit 301 registers information regarding the subscriber device40-1 in the management DB 350. The connection request includesconnection source information, connection destination information, thetype of a signal to be transmitted, and the like. For example, addressinformation such as a Medium Access Control (MAC) address is used as theconnection source information. For example, destination addressinformation is used as the connection destination information. As thetype of a signal to be transmitted, for example, a service, a modulationmethod, or the like is used. The wavelength controller 310 registers theconnection source information in the management DB 350 on the basis ofthese pieces of information. Consequently, identification of a user whouses the subscriber device 40-1 and the fact that a wavelength that canbe used by the subscriber device 40-1 is free are set in the userwavelength table. The wavelength controller 310 calculates an optimumpath between the subscriber device 40-1 and the communicationdestination such as between the ground A and the ground B in comparisonwith the connection information stored in the management DB 350. Thewavelength controller 310 searches for a free wavelength indicated bythe inter-station wavelength table according to the calculated path. Thewavelength controller 310 selects a wavelength to be used by thesubscriber device 40-1 from among the free wavelengths and transmitsinformation regarding the selected wavelength to the control unit 230(step S5).

Another subscriber device 40 that is a communication destination of thesubscriber device 40-1 will be referred to as a communicationdestination subscriber device 40. In this case, the wavelengthcontroller 310 selects a transmission wavelength that is a wavelengthused by the subscriber device 40-1 to transmit an optical signal to thecommunication destination subscriber device 40 and a receptionwavelength that is a wavelength used by the subscriber device 40-1 toreceive an optical signal from the communication destination subscriberdevice 40. The wavelength controller 310 transmits the selectedtransmission wavelength and reception wavelength to the control unit 230as wavelengths to be used by the subscriber device 40-1. In a case wherethe subscriber device 40-1-performs only transmission to thecommunication destination subscriber device 40, the wavelengthcontroller 310 does not have to select the reception wavelength. In acase where the subscriber device 40-1-performs only reception from thecommunication destination subscriber device 40, the wavelengthcontroller 310 does not have to select the transmission wavelength.

The control unit 230 transmits wavelength information as follows. Thewavelength tunable transmitter 233 of the control unit 230 transmits awavelength instruction in which the information regarding the wavelengthselected by the wavelength controller 310 is set, by using an opticalsignal having a wavelength indicating an address to the subscriberdevice 40-1. In a case where the wavelength instruction is transmittedby using an optical signal, the optical SW 210 outputs the opticalsignal input from a port connected to the wavelength tunable transmitter233 of the control unit 20 or via the monitoring unit, or from a portconnected to the communication unit in a case where the communicationunit is used, to the transmission line 522 connected to the subscriberdevice 40-1. The wavelength multiplexer/demultiplexer 220 enters theoptical signal input from the optical SW 210 via the transmission line522 into the transmission line 501. The subscriber device 40-1 receivesthe optical signal transmitted through the transmission line 501. Thewavelength may be branched in the middle of the path, or may bedifferent from the setting as long as the wavelength reaches thesubscriber device 40. If there is no multiplexer/demultiplexer or thelike that demultiplexes according to the wavelength between the controlunit 20 and the subscriber device 40, the wavelength of the signal to betransmitted does not have to be changed. In a case where thetransmission wavelength is set in the instruction using the receivedoptical signal, the subscriber device 40-1 sets a wavelength of theoptical transceiver 41 according to the wavelength instruction (stepS6). That is, the subscriber device 40-1 sets the wavelength of theoptical transceiver 41 (wavelength tunable light source 451) such thatan optical signal is transmitted by using the transmission wavelengthset in the wavelength instruction. In a case where the receptionwavelength is set in the wavelength instruction, the subscriber device40-1 sets the optical transceiver 41 (the wavelength tunable filter 453)to receive a wavelength signal having the reception wavelength.

In a case where an optical signal is transmitted, the opticaltransceiver 41 of the subscriber device 40-1 transmits a notificationsignal for notifying that the wavelength has been set by an opticalsignal having the designated wavelength. Similarly to a request signal,the notification signal is transmitted to the control unit 230 via theoptical SW 210, the monitoring unit 260, or the communication unit. Onthe basis of the received notification signal, the control unit 230checks whether the designated wavelength is set correctly, whether theoutput power is sufficient, and the like (step S7). The control unit 230checks whether or not a value of the notification signal is a value asdesignated. In a case where an optical signal is received, the controlunit 230 may perform checking with a measurement value of the opticalsignal. In a case of determining that there is no problem as a result ofthe checking, the control unit 230 transmits a permission notificationindicating permission to start communication to the subscriber device40-1 by using an optical signal. The permission notification istransmitted to the subscriber device 40-1, similar to the wavelengthinstruction.

The optical SW controller 320 transmits connection information of theoptimum port in the optical SW 210 to the optical SW 210 according to atransmission destination of the subscriber device 40-1. The optical SW210 sets an uplink port and a downlink port of the subscriber device40-1 according to an instruction from the optical SW controller 320 onthe basis of the connection information (step S8).

The optical access system 100 controls a timing such that path switchingin the optical SW 210 is performed after the permission to startcommunication is transmitted from the control unit 230 to the subscriberdevice 40-1. For example, it is assumed that the time required for pathswitching of the optical SW 210 is known in advance. In this case, thecontrol unit 230 waits for the time required for the optical SW 210 toactually switch paths after receiving the path switching instructionuntil the subscriber device 40-1 actually starts communication afterreceiving the permission to start communication, and then gives aninstruction for starting communication. After the communication isstarted, the monitoring unit 260 of the GW 200 checks a communicationstatus between the opposing subscriber devices (step S9). The monitoringunit 260 notifies the OPS 300 of the check result. In a case where thecheck is NG, the control unit 230 or the OPS 300 performs a causeisolation procedure.

The connection request transmitted by the subscriber device 40-1 and thecontrol signal transmitted by the control unit 230 to the subscriberdevice 40-1 are optical signals lower in speed than the main signal. Asthe control signal, for example, a protocol-free control signal (controlmethod) represented by an AMCC may be used.

The control unit or the OPS 300 instructs the communication destinationsubscriber device 40 to use the transmission wavelength of thesubscriber device 40-1 as a reception wavelength of the communicationdestination subscriber device 40 and use the reception wavelength of thesubscriber device 40-1 as a transmission wavelength of the communicationdestination subscriber device 40. For example, in the control unit 301that controls the optical GW 200 in which the communication destinationsubscriber device 40 is accommodated, the wavelength controller 310instructs the control unit 230 to transmit a wavelength instruction inwhich the reception wavelength and the transmission wavelength of thecommunication destination subscriber device 40 are set. Thecommunication destination subscriber device 40 receives the wavelengthinstruction from the control unit 230 by using a control signal, andsets the reception wavelength and the transmission wavelength in theoptical transceiver 41 according to the received wavelength instruction.That is, in a case where the transmission wavelength is set in thewavelength instruction, the communication destination subscriber device40 sets ae wavelength of the optical transceiver 41 (wavelength tunablelight source 451) such that an optical signal is transmitted by usingthe transmission wavelength. In a case where the reception wavelength isset in the wavelength instruction, the communication destinationsubscriber device 40 sets the optical transceiver 41 (wavelength tunablefilter 453) to receive a wavelength signal having the receptionwavelength.

The optical access system 100 may transmit and receive information to beregistered in the management DB 350 through the user application betweenthe new subscriber device 40-1 and the control unit 301 withoutperforming the user application in step S1. Consequently, the subscriberdevice 40-1 can communicate with another subscriber device 40 withoutperforming user application. Transmission and reception of informationbetween the subscriber device 40-1 and the control unit 301 areperformed via the control unit 230 by using, for example, an AMCC.

The operation when the new subscriber device is connected has beendescribed above. Next, a normal communication operation after a newsubscriber device is connected will be described by exemplifying a casewhere the subscriber device 40-2 in FIG. 38 performs communication.

First, an uplink optical signal output from the subscriber device 40-2described for the uplink communication is transmitted to the optical GW200 via the transmission line 501. The wavelengthmultiplexer/demultiplexer 220 of the optical GW 200 separates the inputoptical signal into an uplink optical signal and a downlink opticalsignal according to wavelengths. The uplink optical signal demultiplexedby the wavelength multiplexer/demultiplexer 220 is input to the opticalSW 210 via the transmission line 521. The optical SW 210 connects theport to which the uplink optical signal has been input from thewavelength multiplexer/demultiplexer 220 to another port correspondingto a path to a transfer destination on the path to a communicationdestination of the subscriber device 40-2, and outputs the opticalsignal. In a case where a wavelength is used as the destinationinformation, the optical SW 210 is connected to another portcorresponding to the transfer destination on the path to thecommunication destination specified by the wavelength allocated to thesubscriber device 40-2 and outputs the optical signal. The uplink signaloutput from the optical SW 210 is multiplexed with an optical signalhaving a different wavelength transmitted by another subscriber device40 in the multiplexer 241 and transmitted to another station (forexample, the ground B) via one transmission line 511. Each multiplexer241 multiplexes wavelength channels for each station such as the groundB and the ground C. It is also possible to use the same wavelengthbetween the ground B and the ground C by separating the transmissionline 511 to the ground B and the transmission line 511 to the ground C.

Next, the downlink communication will be described. The downlinkcommunication is communication from the ground B or C toward thesubscriber device 40. A downlink optical signal is sent to the opticalGW 200 via one transmission line 512. The demultiplexer 242 of theoptical GW 200 demultiplexes the downlink optical signal transmittedthrough the transmission line 512 according to wavelengths. Thedemultiplexer 242 inputs the demultiplexed light to a downlink portcorresponding to the wavelength of the demultiplexed light via thetransmission line 542. The optical SW 210 connects the port to which thedownlink optical signal is input from the demultiplexer 242 to anotherport corresponding to the wavelength, and outputs the optical signal.The wavelength multiplexer/demultiplexer 220 separates the opticalsignal input from the optical SW 210 via the transmission line 522 intoan uplink optical signal and a downlink optical signal according towavelengths. The downlink optical signal demultiplexed by the wavelengthmultiplexer/demultiplexer 220 is input to the subscriber device 40-2 viathe transmission line 501. The wavelength channels transmitted from theoptical GW 200 to the respective stations (for example, the grounds B,and C) are assumed to be the same wavelength band, but differentwavelength bands may be used for each station.

The monitoring unit 260 of the optical GW 200 receives light branched bythe branching unit 250. The light branched by the branching unit 250 isan optical signal transmitted and received by each subscriber device 40.The monitoring unit 260 monitors the received optical signal to monitora signal transmitted and received by each subscriber device 40. In acase where an abnormality such as a wavelength shift, a decrease inoutput, or a communication abnormality is detected through themonitoring, the monitoring unit 260 transmits an abnormality detectionsignal to the control unit 301. The optical SW controller 320 of thecontrol unit 301 controls the optical SW 210 such that the targetsubscriber device 40 is connected to the control unit 230 again. Thecontrol unit 301 performs an allocation process of a new wavelengthdifferent from the wavelength used when the abnormality is detected,similarly to when the new subscriber device 40 is connected.Consequently, in a case where an optical signal having a changedwavelength is input from the subscriber device 40, the optical SW 210inputs the input optical signal to the port specified by the wavelengthbefore the change by the subscriber device 40.

(First Configuration Example of Optical Access System 100)

Although the optical GW 200 illustrated in FIG. 38 performs wavelengthmultiplexing, it is not necessary to perform wavelength multiplexing asillustrated in FIGS. 43 and 44 . FIG. 43 is a diagram illustrating aconfiguration example of an optical access system 101. The opticalaccess system 101 illustrated in FIG. 43 is different from the opticalaccess system 100 illustrated in FIG. 38 in that a GW 201 is providedinstead of the GW 200. The GW 201 is different from the GW 200 in thatit includes a wavelength multiplexer/demultiplexer 243 and a branchingunit 250 a instead of the multiplexer 241, the demultiplexer 242, andthe branching unit 250. The GW 201 is connected to a communicationdevice of a station at another ground via a transmission line 503. Onetransmission line 503 transmits an uplink signal and a downlink signalto and from any ground.

The wavelength multiplexer/demultiplexer 243 separates an input opticalsignal into an uplink optical signal and a downlink optical signalaccording to wavelengths. The wavelength multiplexer/demultiplexer 243separates an uplink optical signal input from the optical SW 210 via atransmission line 543-1, and transmits the signal to another ground or ahigher network via the transmission line 503. The wavelengthmultiplexer/demultiplexer 243 separates a downlink optical signal inputfrom another ground via the transmission line 503, and outputs thesignal to the optical SW 210 via a transmission line 543-2.

The branching unit 250 a is provided in the transmission line 503. Thebranching unit 250 a includes a power splitter 251 a. The power splitter251 a branches uplink and downlink optical signals transmitted throughthe transmission line 503. The power splitter 251 a inputs the brancheduplink optical signal to the port of the optical SW 210 via thetransmission line 551 a, and inputs the branched downlink optical signalto the port of the optical SW 210 via the transmission line 551 b. Theoptical SW 210 outputs the optical signal input from the port connectedto the transmission line 551 a and the optical signal input from theport connected to the transmission line 551 b from the port connected tothe transmission line 560. Consequently, the wavelength demultiplexer261 of the monitoring unit 260 receives the optical signal branched bythe branching unit 250 a.

(Second Configuration Example of Optical Access System 100)

FIG. 44 is a diagram illustrating a configuration example of an opticalaccess system 102. An optical access system 102 illustrated in FIG. 44is different from the optical access system 101 illustrated in FIG. 43in that an optical GW 202 is provided instead of the optical GW 201. Theoptical GW 202 is different from the optical GW 201 in that it includesa wavelength multiplexer/demultiplexer 244, a wavelengthmultiplexer/demultiplexer 245, and a branching unit 250 b instead of thewavelength multiplexer/demultiplexer 243 and the branching unit 250 a.

The wavelength multiplexer/demultiplexer 244 separates an uplink opticalsignal and a downlink optical signal according to wavelengths. Thewavelength multiplexer/demultiplexer 244 inputs the uplink opticalsignal input from the optical SW 210 via the transmission line 544 tothe wavelength multiplexer/demultiplexer 245 via the transmission line545. The wavelength multiplexer/demultiplexer 244 inputs the downlinkoptical signal input from the wavelength multiplexer/demultiplexer 245via the transmission line 546 to the optical SW 210 via the transmissionline 544.

The wavelength multiplexer/demultiplexer 245 separates an uplink opticalsignal and a downlink optical signal according to wavelengths. Thewavelength multiplexer/demultiplexer 245 transmits the uplink opticalsignal input from the wavelength multiplexer/demultiplexer 245 via thetransmission line 545 to another ground or a higher network via thetransmission line 503. The wavelength multiplexer/demultiplexer 245inputs the downlink optical signal received via the transmission line503 to the wavelength multiplexer/demultiplexer 244 via the transmissionline 546.

The branching unit 250 b includes a power splitter 251 b and a powersplitter 252 b. The power splitter 251 b branches an uplink opticalsignal transmitted through the transmission line 545. The power splitter251 b inputs the branched uplink optical signal to the port of theoptical SW 210 via the transmission line 551 b. The power splitter 252 bbranches a downlink optical signal transmitted through the transmissionline 546. The power splitter 252 b inputs the branched downlink opticalsignal to the port of the optical SW 210 via the transmission line 552b. The optical SW 210 outputs the optical signal input from a portconnected to the transmission line 551 b and the optical signal inputfrom the port connected to the transmission line 552 b from the portconnected to the transmission line 560. Consequently, the optical signalbranched by the branching unit 250 b is input to the wavelengthdemultiplexer 261 of the monitoring unit 260.

The monitoring unit 260 described above has a receiver configurationincluding the wavelength demultiplexer 261 and the optical receiver 262for each wavelength. The monitoring unit 260 may include a wavelengthtunable optical receiver instead of the receiver configuration. Thetransceiver of the control unit may have a transmitter that does nottransmit a signal having a variable wavelength, or may have a receiverconfiguration not including a wavelength demultiplexer. An example ofsuch a configuration will be described with reference to FIG. 45 .

(Third Configuration Example of Optical Access System 100)

FIG. 45 is a diagram illustrating a configuration example of an opticalaccess system 103. The optical access system 103 illustrated in FIG. 45is different from the optical access system 100 illustrated in FIG. 38in that an optical GW 203 is provided instead of the optical GW 200. Theoptical GW 203 is different from the optical GW 200 in that a controlunit 235 and a monitoring unit 265 are provided instead of the controlunit 230 and the monitoring unit 260. The control unit 235 includes anoptical receiver 236 and an optical transmitter 237 that does nottransmit a signal having a variable wavelength. The monitoring unit 265includes a wavelength tunable optical receiver 266. The monitoring unit265 may be replaced with any one of the monitoring units 60 to 60 hdescribed above.

(Fourth Configuration Example of Optical Access System 100)

The monitoring unit may be connected via an optical SW different fromthe above-described optical SW. An example of such a configuration willbe described with reference to FIG. 46 . FIG. 46 is a diagramillustrating a configuration example of an optical access system 104.The optical access system 104 illustrated in FIG. 46 is different fromthe optical access system 103 illustrated in FIG. 45 in that an opticalGW 204 is provided instead of the optical GW 203. The optical GW 204 isdifferent from the optical GW 203 in that an optical SW 211 is furtherprovided and that the monitoring unit 265 is connected to the optical SW211.

An uplink optical signal separated from the transmission line 511 by thepower splitter 251 of the branching unit 250 is input to the optical SW211 via the transmission line 555, and a downlink optical signalseparated from the transmission line 512 by the power splitter 252 isinput to the optical SW 211 via the transmission line 555. The opticalSW 211 is, for example, a small optical SW. The number of ports of theoptical SW 211 is one on the monitoring unit 260 side and 2M on the sideto which a monitoring target optical signal is input. 2M is twice thenumber M of the subscriber devices 40 connected to the optical GW 204.Monitoring units may be prepared by the number of connected groundswithout using the small optical SW, and signals transmitted to andreceived from all the grounds may be monitored for each ground.

In the present configuration example, communication is performed betweena plurality of subscriber devices connected to the same optical GW byusing a return transmission line. In the following description, adescription will focus on differences from the above configurationexamples.

(Fifth Configuration Example of Optical Access System 100)

FIG. 47 is a diagram illustrating a configuration example of an opticalaccess system 105. The optical access system 105 illustrated in FIG. 47is different from the optical access system 103 illustrated in FIG. 45in that an optical GW 205 is provided instead of the optical GW 203. Theoptical GW 205 is different from the optical GW 203 in that amultiplexer 247 and a demultiplexer 248 corresponding to the ground Awhere the optical GW 205 is installed are further provided. Themultiplexer 247 and the demultiplexer 248 are connected via atransmission line 547. The transmission line 547 is a returntransmission line.

Similarly to the multiplexer 241, the multiplexer 247 multiplexes uplinkoptical signals having different wavelengths respectively output fromthe plurality of transmission lines 541 by the optical SW 210, andoutputs the multiplexed signal to the transmission line 547. Similarlyto the demultiplexer 242, the demultiplexer 248 demultiplexes a downlinkoptical signal input from the transmission line 547 according towavelengths. The demultiplexer 248 inputs the respective demultiplexeddownlink optical signals to the optical SW 210 via a plurality oftransmission lines 542 connected to downlink ports corresponding towavelengths of the optical signals. The branching unit 250 is providedin the transmission line 547.

In the above configuration example, the subscriber device connected tothe ground A is connected to a port for connection to the ground B orthe ground C via the optical SW. In the present configuration example,another set that is the same as the combination of the multiplexer 241and the demultiplexer 242 connected to the ground B or the ground C isadded. The added set includes the multiplexer 247 and the demultiplexer248. An output port of the added multiplexer 247 and an input port ofthe added demultiplexer 248 are connected via the transmission line 547.With this configuration, a signal output from the subscriber device 40can be input to the optical SW 210 again. Consequently, the optical GW205 returns an optical signal output from a certain subscriber device 40and enters the optical signal the optical SW 210 again as a downlinksignal. By inputting this return signal to another subscriber device 40in the optical SW 210, return communication, that is, communicationbetween the subscriber devices 40 connected to the same optical GW 205can be performed.

For example, a state in which the subscriber device 40-2 and thesubscriber device 40-M communicate with each other will be described. Itis assumed that each of K (where K is an integer of 2 or more) uplinkports of the optical SW 210 corresponding to the ground A is connectedto the multiplexer 247 via the transmission line 541, and each of Kdownlink ports of the optical SW 210 corresponding to the ground A isconnected to the demultiplexer 248 via the transmission line 542. It isassumed that the k-th (where k is an integer of 1 or more and K or less)uplink port and downlink port among the K downlink ports and uplinkports corresponding to the ground A correspond to a wavelength λk. Theuplink optical signal having the wavelength λ1 output from thesubscriber device 40-2 is input to the first uplink port correspondingto the ground A. The input optical signal is returned by thetransmission line 547 and is input to the optical SW 210 again as adownlink optical signal from the first downlink port corresponding tothe ground A. The optical SW controller 320 sets a path in the opticalSW 210 such that the optical signal is transmitted to the subscriberdevice 40-M according to the wavelength. Similarly, the uplink opticalsignal having the wavelength λk output from the subscriber device 40-Mis input to the k-th uplink port corresponding to the ground A. Theinput optical signal is returned by the transmission line 547 and isinput to the optical SW 210 again as a downlink optical signal from thek-th downlink port corresponding to the ground A. The optical SWcontroller 320 sets a path in the optical SW 210 such that the opticalsignal is transmitted to the subscriber device 40-2 according to thewavelength. Consequently, communication is performed between thesubscriber device 40-2 and the subscriber device 40-M.

(Sixth Configuration Example of Optical Access System 100)

Another configuration of the present configuration example will bedescribed with reference to FIGS. 48 and 49 . FIG. 48 is a diagramillustrating a configuration example of an optical access system 106.The optical access system 106 illustrated in FIG. 48 is different fromthe optical access system 105 illustrated in FIG. 47 in that an opticalGW 206 is provided instead of the optical GW 205. The optical GW 206 isdifferent from the optical GW 205 in that the multiplexer 247 and thedemultiplexer 248 are not provided, and the uplink port and the downlinkport for the ground A of the optical SW 210 are directly connected viathe transmission line 548 without wavelength multiplexing, so that asignal is returned.

(Seventh Configuration Example of Optical Access System 100)

FIG. 49 is a diagram illustrating a configuration example of an opticalaccess system 107. The optical access system 107 illustrated in FIG. 49is different from the optical access system 105 illustrated in FIG. 47in that an optical GW 207 is provided instead of the optical GW 205. Theoptical GW 207 is different from the optical GW 205 in that a powersplitter 270 is provided instead of the demultiplexer 248. The powersplitter 270 branches a downlink optical signal input from themultiplexer 247 via the transmission line 547 into a plurality ofsignals, and inputs the plurality of signals to the optical SW 210 viathe plurality of transmission lines 542.

A power splitter may be provided at a subsequent stage with respect tothe demultiplexer 248 of the optical GW 205 in FIG. 47 . The powersplitter branches the optical signal demultiplexed by the demultiplexer248 into a plurality of signals, and inputs the plurality of signals todifferent ports of the optical SW 210. As described above, multicastcommunication of return communication can be performed.

Although the difference from the optical access system 103 has beendescribed above, the difference may also be applied to the opticalaccess systems 100, 101, and 102.

(Eighth Configuration Example of Optical Access System 100)

An optical access system of the present configuration example performsmulticast communication. In the present configuration example, adescription will focus on differences.

First, multicast in downlink communication will be described withreference to FIG. 50 . FIG. 50 is a diagram illustrating a configurationexample of an optical access system 108. The optical access system 108illustrated in FIG. 50 is different from the optical access system 107illustrated in FIG. 49 in that an optical GW 208 is provided instead ofthe optical GW 207. The optical GW 208 is different from the optical GW207 in that a transmission line 549 that connects a return port of theoptical SW 210 is further provided.

A case where a downlink optical signal transmitted from the ground C ismulticasted will be described. The optical SW controller 320 performscontrol such that a port to which the downlink optical signal from theground C is input is connected to a return port to which thetransmission line 549 is connected according to a wavelength.Consequently, the downlink optical signal from the ground C istransmitted through the transmission line 549 and is input again to theoptical SW 210 as an uplink signal of the ground A. The optical SWcontroller 320 performs control such that the downlink optical signalinput from the return port is input to the uplink signal port for theground A. Consequently, the optical signal returned through thetransmission line 549 and input to the optical SW 210 is output to theport connected to the multiplexer 247. The multiplexer 247 multiplexesthe optical signals output from the optical SW 210 via the plurality ofrespective transmission lines 541 and outputs the multiplexed opticalsignal to the transmission line 547. The optical signal output to thetransmission line 547 is branched into a plurality of optical signals bythe power splitter 270. The power splitter 270 inputs the plurality ofbranched optical signals to the optical SW 210 as downlink signals ofthe ground A via the plurality of transmission lines 542. The optical SW210 outputs the optical signal input from each transmission line 542 toa port connected to the subscriber device 40 according to thewavelength. This enables multicast of downlink signals.

(Ninth Configuration Example of Optical Access System 100)

Next, multicast of uplink communication will be described with referenceto FIG. 51 . FIG. 51 is a diagram illustrating a configuration exampleof an optical access system 109. The optical access system 109illustrated in FIG. 51 is different from the optical access system 103illustrated in FIG. 45 in that an optical GW 209 is provided instead ofthe optical GW 203. The optical GW 209 is different from the optical GW203 in that a transmission line 570 that connects a return port to theoptical SW 210 and a power splitter 271 for multicast are provided. Thepower splitter 271 is connected to the optical SW 210 via thetransmission line 572 and the plurality of transmission lines 573.

A case where an uplink optical signal transmitted from the ground A ismulticasted will be described. The optical SW controller 320 performscontrol such that a port to which the uplink optical signal from theground A is input is connected to a return port to which thetransmission line 570 is connected according to a wavelength.Consequently, the uplink optical signal from the ground A is transmittedthrough the transmission line 570 and is input to the optical SW 210again. The optical SW controller 320 performs control such that theoptical signal input from the return port is output to the portconnected to the power splitter 271. Consequently, the optical signalthat is returned through the transmission line 570 and is input to theoptical SW 210 is output to the transmission line 572. The opticalsignal output to the transmission line 572 is branched into a pluralityof optical signals by the power splitter 271. The power splitter 271inputs the plurality of branched optical signals to the optical SW 210as uplink signals via the plurality of transmission lines 573. Theoptical SW 210 outputs the optical signal input from each transmissionline 573 to the port connected to the ground B or the ground C accordingto the wavelength. This enables multicast of the uplink signal.

(Tenth Configuration Example of Optical Access System 100)

Next, a configuration in which point to multipoint communicationincluding uplink communication is performed while multicasting downlinkcommunication will be described with reference to FIG. 52 . FIG. 52 is adiagram illustrating a configuration example of an optical access system110. The optical access system 110 illustrated in FIG. 52 is differentfrom the optical access system 103 illustrated in FIG. 45 in that anoptical GW 2010 is provided instead of the optical GW 203. The opticalGW 2010 is different from the optical GW 203 in that transmission lines574 and 575 connecting a return port to the optical SW 210 and powersplitters 272 and 273 are further provided. The power splitter 272 isconnected to the optical SW 210 via the transmission line 581 and theplurality of transmission lines 582. The power splitter 273 is connectedto the optical SW 210 via the plurality of transmission lines 583 andthe transmission line 584.

A case where a downlink optical signal transmitted from the ground C ismulticasted will be described. The optical SW controller 320 performscontrol such that a port to which the downlink optical signal from theground C is input is connected to a return port to which thetransmission line 574 is connected according to a wavelength.Consequently, the downlink optical signal from the ground C istransmitted through the transmission line 574 and is input again to theoptical SW 210 as an uplink signal of the ground A. The optical SWcontroller 320 performs control such that the downlink optical signalinput from the return port is output to the port to which the powersplitter 272 is connected. Consequently, the optical signal that isreturned through the transmission line 574 and is input to the opticalSW 210 is output to the transmission line 581. The optical signal outputto the transmission line 581 is branched into a plurality of opticalsignals by the power splitter 272. The power splitter 272 inputs theplurality of branched optical signals to the optical SW 210 as downlinksignals via the plurality of transmission lines 582. The optical SW 210outputs the optical signal input from each transmission line 582 to aport connected to the subscriber device 40 according to the wavelength.This enables multicast of downlink signals.

A case where an uplink optical signal transmitted from the ground A istransmitted to the ground C will be described. The optical SW controller320 performs control such that a port to which the uplink optical signalfrom the ground A is input is connected to a port to which the powersplitter 273 is connected according to a wavelength. Consequently, theuplink optical signal from the ground A is output to the transmissionline 583. The optical signals respectively output to the plurality oftransmission lines 583 are multiplexed by the power splitter 273. Thepower splitter 273 inputs the multiplexed optical signal to the opticalSW 210 via the transmission line 584. The optical SW 210 performscontrol such that the optical signal input from the transmission line584 is input to the return port to which the transmission line 575 isconnected. Consequently, the optical signal is transmitted through thetransmission line 575 and is input to the optical SW 210 again. Theoptical SW 210 outputs the optical signal input from the transmissionline 575 to the multiplexer 241 connected to the ground C according tothe wavelength.

As described above, by providing two sets of configurations using apower splitter for multicast, not only downlink multicast communicationbut also point to multipoint communication including uplinkcommunication can be performed.

(Eleventh Configuration Example of Optical Access System 100)

In the present configuration example, communication is performed withoutseparating an uplink signal and a downlink signal. Hereinafter, adescription will focus on differences from each of the aboveconfiguration examples.

FIG. 53 is a diagram illustrating a configuration example of an opticalaccess system 111. The optical access system 111 illustrated in FIG. 53is different from the optical access system 105 illustrated in FIG. 47in that an optical GW 2011 is provided instead of the optical GW 205.The optical GW 2011 is different from the optical GW 205 in that thewavelength multiplexer/demultiplexer 220 is not provided, a wavelengthmultiplexer/demultiplexer 249 and a branching unit 253 are providedinstead of the multiplexer 241, the demultiplexer 242, and the branchingunit 250, and a wavelength multiplexer/demultiplexer 238 is furtherprovided.

The wavelength multiplexer/demultiplexer 249 is connected to the opticalSW 210 via a plurality of transmission lines 585. The wavelengthmultiplexer/demultiplexer 249 multiplexes uplink optical signals havingdifferent wavelengths respectively output from the plurality oftransmission lines 585 by the optical SW 210, and outputs themultiplexed signal to the transmission line 504 connected to any otherground. The wavelength multiplexer/demultiplexer 249 demultiplexes adownlink optical signal input from another ground via the transmissionline 504 according to wavelengths. The wavelengthmultiplexer/demultiplexer 249 inputs the respective demultiplexeddownlink optical signals to the optical SW 210 via a plurality oftransmission lines 585 connected to the uplink ports corresponding tothe wavelengths of the optical signals.

The branching unit 253 includes a power splitter 254. The power splitter254 branches an uplink optical signal and a downlink optical signaltransmitted through the transmission line 504. The power splitter 254inputs the branched uplink optical signal to the port of the optical SW210 via the transmission line 586, and inputs the branched downlinkoptical signal to the port of the optical SW 210 via the transmissionline 587. The optical SW 210 outputs the optical signal input from aport connected to the transmission line 586 or the transmission line 587to a port connected to the transmission line 560.

The wavelength multiplexer/demultiplexer 238 is connected to the opticalSW 210 via the transmission line 534, and is connected to the controlunit 235 via the transmission line 531 and the transmission line 533.The wavelength multiplexer/demultiplexer 238 separates the input opticalsignal into an uplink optical signal and a downlink optical signalaccording to wavelengths. The wavelength multiplexer/demultiplexer 238outputs the uplink optical signal input from the optical SW 210 via thetransmission line 534 to the control unit 235 via the transmission line531. The wavelength multiplexer/demultiplexer 238 outputs the downlinkoptical signal input from the control unit 235 via the transmission line533 to the optical SW 210 via the transmission line 534.

As described above, the optical GW 2011 has a configuration in whichthere is no wavelength multiplexer/demultiplexer between the optical SW210 and the subscriber device 40 and an uplink signal and a downlinksignal are not separated. Consequently, the number of ports used for theoptical SW 210 can be greatly reduced, and an amount of information tobe managed can be greatly reduced. As illustrated in FIG. 54 , a portionthat separates an optical signal to the monitoring unit 265 may have aconfiguration illustrated in FIG. 44 .

(Twelfth Configuration Example of Optical Access System 100)

FIG. 54 is a diagram illustrating a configuration example of an opticalaccess system 112 according to the present embodiment. An optical GW2012 of the optical access system 112 illustrated in FIG. 54 includes abranching unit 255 instead of the branching unit 253 included in theoptical GW 2011 illustrated in FIG. 53 . The branching unit 255 includesa wavelength multiplexer/demultiplexer 256, a wavelengthmultiplexer/demultiplexer 257, a power splitter 258, and a powersplitter 259.

The wavelength multiplexer/demultiplexer 256 separates an input opticalsignal into an uplink optical signal and a downlink optical signalaccording to wavelengths. The wavelength multiplexer/demultiplexer 256outputs the uplink optical signal input from the wavelengthmultiplexer/demultiplexer 249 to the wavelengthmultiplexer/demultiplexer 257 via the transmission line 588. Thewavelength multiplexer/demultiplexer 256 outputs the downlink opticalsignal input from the wavelength multiplexer/demultiplexer 257 via thetransmission line 589 to the wavelength multiplexer/demultiplexer 249.

The wavelength multiplexer/demultiplexer 257 separates an optical signalinto an uplink optical signal and a downlink optical signal according towavelengths. The wavelength multiplexer/demultiplexer 257 outputs theuplink optical signal input from the wavelengthmultiplexer/demultiplexer 256 via the transmission line 588 to thetransmission line 504. The wavelength multiplexer/demultiplexer 257inputs a downlink optical signal received from another ground via thetransmission line 504 to the wavelength multiplexer/demultiplexer 256via the transmission line 589.

The power splitter 258 branches an uplink optical signal transmittedthrough the transmission line 588, and inputs the branched signal to theport of the optical SW 210 via the transmission line 586. The powersplitter 259 branches a downlink optical signal transmitted through thetransmission line 589, and inputs the branched signal to the port of theoptical SW 210 via the transmission line 587. The optical SW 210 outputsthe optical signal input from a port connected to the transmission line586 or the transmission line 587 to a port connected to the transmissionline 560.

The optical GW 2011 illustrated in FIG. 53 performs wavelengthmultiplexing. However, as illustrated in FIG. 55 , a signal to betransmitted to each of the stations (the ground B and the ground C) maybe transmitted through individual transmission lines without performingwavelength multiplexing.

(Thirteenth Configuration Example of Optical Access System 100)

FIG. 55 is a diagram illustrating a configuration example of an opticalaccess system 113. The optical access system 113 illustrated in FIG. 55is different from the optical access system 101 illustrated in FIG. 43in that an optical GW 2013 is provided instead of the optical GW 201.The optical GW 2013 is different from the optical GW 201 in that thewavelength multiplexer/demultiplexer 220 and the wavelengthmultiplexer/demultiplexer 243 are not provided, and the control unit235, the wavelength multiplexer/demultiplexer 238, and the monitoringunit 265 illustrated in FIG. 53 are provided instead of the control unit230 and the monitoring unit 260. A port of the optical SW 210 connectedto the transmission line 503 outputs an uplink optical signal andreceives a downlink optical signal.

(Fourteenth Configuration Example of Optical Access System 100)

The branching unit 250 a of the optical GW 2013 may have a configurationillustrated in FIG. 56 . FIG. 56 is a diagram illustrating aconfiguration example of an optical access system 114. An optical GW2014 of the optical access system 114 illustrated in FIG. 56 has aconfiguration similar to that of the branching unit 255 illustrated inFIG. 54 instead of the branching unit 250 a included in the optical GW2013 illustrated in FIG. 55 .

(Fifteenth Configuration Example of Optical Access System 100)

The present configuration example enables control of a subscriber devicein communication. Hereinafter, a description will focus on differencesfrom each of the above configuration examples.

FIG. 57 is a diagram illustrating a configuration example of an opticalaccess system 115. The optical access system 115 illustrated in FIG. 57is different from the optical access system 104 illustrated in FIG. 46in that an optical GW 2015 is provided instead of the optical GW 204.The optical GW 2015 is different from the optical GW 204 in that amonitoring unit 267 is connected to the optical SW 211 instead of themonitoring unit 265.

The monitoring unit 267 includes a wavelength tunable receiver 268 and awavelength tunable transmitter 269. The monitoring unit 267 can receivean optical signal having any wavelength with the wavelength tunablereceiver 268 and can transmit an optical signal having any wavelengthwith the wavelength tunable transmitter 269. The optical GW 2015includes a control unit 235. When the optical GW 2015 is connected tothe subscriber device 40, the optical GW 2015 performs a connectionprocess (registration, wavelength allocation, and the like) for thesubscriber device 40 by using the control unit 235, and starts normalcommunication.

Here, a state in which the subscriber device 40-1 is connected to theground B is considered. The subscriber device 40-1 cannot communicatewith the control unit 235 because normal communication is beingperformed. Therefore, by providing the monitoring unit 267 connected tothe optical SW 211 that is a small optical SW, it is possible not onlyto monitor a communication state of the subscriber device 40-1 but alsoto give instructions for various settings of the subscriber device 40-1.That is, an optical signal separated by the power splitter 251 is outputto the optical SW 211 via the transmission line 555. The optical SW 211outputs the input optical signal to the monitoring unit 267. Themonitoring unit 267 performs monitoring by using the optical signalreceived from the optical SW 211 by the wavelength tunable receiver 268,and further receives a control signal superimposed on the receivedoptical signal. The wavelength tunable transmitter 269 of the monitoringunit 267 transmits a control signal to the subscriber device 40 by usingan optical signal. The optical SW 211 outputs the optical signal inputfrom the wavelength tunable transmitter 269 to a port corresponding to awavelength. The power splitter 251 multiplexes the control signal inputfrom the optical SW 211 via the transmission line 556 with the opticalsignal transmitted through the transmission line 512. With thisconfiguration, even in a state in which the subscriber device 40-1 isperforming normal communication, it is possible to receive a connectiondestination change request or the like from the subscriber device 40-1,transmit a control signal, and perform wavelength switching or the likeon the subscriber device 40-1.

In communication of a control signal between the monitoring unit 267 andeach of the subscriber devices 40, a control signal that is slower thanan optical main signal between the subscriber devices and can besuperimposed on the main signal is used. For example, a technique suchas AMCC may be used.

(Sixteenth Configuration Example of Optical Access System 100)

In the present configuration example, electrical processing is performedon an optical signal extracted from the optical SW. Hereinafter, adescription will focus on differences from each of the aboveconfiguration examples.

FIG. 58 is a diagram illustrating a configuration example of an opticalaccess system 116. The optical access system 116 illustrated in FIG. 58is different from the optical access system 105 illustrated in FIG. 47in that an optical GW 2016 is provided instead of the optical GW 202.The optical GW 2016 is different from the optical GW 202 in that anelectrical processing unit 600 is connected.

The electrical processing unit 600 converts an optical signal into anelectrical signal, performs electrical processing on the electricalsignal, converts the electrical signal into an optical signal again, andoutputs the optical signal. The electrical processing unit 600 includesan O/E conversion unit 610, a processing execution unit 620, and an E/Oconversion unit 630. The O/E conversion unit 610 corresponds to the O/Econversion unit 85 in FIG. 13 . The O/E conversion unit 610 converts anoptical signal input from the optical SW 210 into an electrical signaland outputs the electrical signal to the processing execution unit 620.The processing execution unit 620 corresponds to the processingexecution unit 86 and the storage unit 88 in FIG. 13 . The processingexecution unit 620 performs electrical processing on the electricalsignal converted by the O/E conversion unit 610 by a processor such as aCPU or an accelerator reading a program from a storage unit (notillustrated) and executing the program. In this electrical processing, afunction of electrically processing a signal, a function such as an OLT,and the like are realized. The signal processing function is, forexample, code error correction such as FEC. The E/O conversion unit 630corresponds to the E/O conversion unit 87 in FIG. 13 . The E/Oconversion unit 87 converts the electrical signal into an optical signaland outputs the optical signal to the optical SW 210. The O/E conversionunit 610 and the E/O conversion unit 630 are, for example, wavelengthtunable transceivers.

In FIG. 58 , the subscriber device 40-M is an ONU of a PON. Thesubscriber device 40-M is connected to the optical GW 2016 via thetransmission line 501 such as an optical fiber and the power splitter507. The processing execution unit 620 of the electrical processing unit600 has an error correction function, an OLT function, and the like.

The wavelength controller 310 notifies the processing execution unit 620of determination conditions for determining a signal that is a targetsubjected to electrical processing and the type of electrical processingto be performed on the signal. The processing execution unit 620 storesinformation regarding the determination conditions and the type ofelectrical processing reported from the wavelength controller 310.

For example, in step S5 in FIG. 42 , the wavelength controller 310determines whether or not to perform electrical processing oncommunication between the subscriber device 40 (hereinafter, referred toas a request source subscriber device 40) that is a transmission sourceof the connection request and the communication destination subscriberdevice 40. The wavelength controller 310 determines whether or not toperform the electrical processing and, in a case where the electricalprocessing is to be performed, what kind of electrical processing is tobe performed according to a distance between the request sourcesubscriber device 40 and the communication destination subscriber device40 opposing each other, a service to be provided to the request sourcesubscriber device 40 or the communication destination subscriber device40, or the like. In a case where it is determined that electricalprocessing (hereinafter, transmission signal electrical processing) isto be performed on a signal addressed to the communication destinationsubscriber device 40 from the request source subscriber device 40, thewavelength controller 310 allocates a first transmission wavelength anda second transmission wavelength from among free wavelengths. In a casewhere it is determined that electrical processing (hereinafter,reception signal electrical processing) is to be performed on a signaladdressed to the request source subscriber device 40 from thecommunication destination subscriber device 40, the wavelengthcontroller 310 allocates a first reception wavelength and a secondreception wavelength from among free wavelengths.

The first transmission wavelength is a wavelength for routing an opticaltransmission signal that is an optical signal addressed to thecommunication destination subscriber device 40 from the request sourcesubscriber device 40, to the electrical processing unit 600. The secondtransmission wavelength is a wavelength for routing a transmissionsignal subjected to the transmission signal electrical processing by theelectrical processing unit 600 to a port corresponding to thecommunication destination subscriber device 40. The first receptionwavelength is a wavelength for routing a reception signal that is anoptical signal addressed to the request source subscriber device 40 fromthe communication destination subscriber device 40, to the electricalprocessing unit 600. The second reception wavelength is a wavelength forrouting the reception signal subjected to the reception signalelectrical processing by the electrical processing unit 600 to a portcorresponding to the request source subscriber device 40. The firsttransmission wavelength and the second transmission wavelength may bethe same wavelength, or the first reception wavelength and the secondreception wavelength may be the same wavelength.

In a case where it is determined that the transmission signal electricalprocessing is to be performed, the wavelength controller 310 setsinformation regarding the first transmission wavelength as atransmission wavelength in a wavelength instruction to be transmitted tothe request source subscriber device 40. In a case where it isdetermined that the reception signal electrical processing is to beperformed, the wavelength controller 310 sets information regarding thesecond reception wavelength as a reception wavelength in a wavelengthinstruction to be transmitted to the request source subscriber device40.

In a case where it is determined that the transmission signal electricalprocessing is to be performed, the OPS 300 gives an instruction forusing the second transmission wavelength as a reception wavelength ofthe communication destination subscriber device 40. In a case where itis determined that the reception signal electrical processing is to beperformed, the OPS 300 gives an instruction for using the firsttransmission wavelength as a transmission wavelength of thecommunication destination subscriber device 40. For example, in thecontrol unit 301 that controls the optical GW 200 in which thecommunication destination subscriber device 40 is accommodated, thewavelength controller 310 instructs the control unit 230 to transmit awavelength instruction in which the reception wavelength and thetransmission wavelength of the communication destination subscriberdevice 40 are set.

In a case where it is determined that the transmission signal electricalprocessing is to be performed, the wavelength controller 310 generatesfirst instruction information in which determination conditions fordetermining that a signal is a transmission signal addressed to thecommunication destination subscriber device 40 from the request sourcesubscriber device 40, the type of transmission signal electricalprocessing to be performed on the transmission signal, the firsttransmission wavelength, and the second transmission wavelength areassociated with each other. In a case where it is determined that thereception signal electrical processing is to be performed, thewavelength controller 310 generates second instruction information inwhich determination conditions for determining that a signal is areception signal addressed to the request source subscriber device 40from the communication destination subscriber device 40, the type ofreception signal electrical processing to be performed on the receptionsignal, the first reception wavelength, and the second receptionwavelength are associated with each other. The wavelength controller 310transmits an electrical processing execution instruction in which thegenerated first instruction information and second instructioninformation are set to the electrical processing unit 600.

In a case where the transmission signal electrical processing isperformed, the optical SW controller 320 controls the optical SW 210such that a transmission signal having the first transmission wavelengthtransmitted by the request source subscriber device 40 is output to theelectrical processing unit 600, and a transmission signal having thesecond transmission wavelength input from the electrical processing unit600 is output to the transmission line 541 corresponding to thecommunication destination subscriber device 40. In a case where thereception signal electrical processing is performed, the optical SWcontroller 320 controls the optical SW 210 such that a reception signalhaving the first transmission wavelength input from the transmissionline 542 corresponding to the communication destination subscriberdevice 40 is output to the electrical processing unit 600, and areception signal having the second transmission wavelength input fromthe electrical processing unit 600 is output to the transmission line522 corresponding to the request source subscriber device 40.

For example, it is assumed that transmission signal electricalprocessing and reception signal electrical processing are performed onan optical signal between the subscriber device 40-2 and thecommunication destination subscriber device 40 at the ground C. Thetransmission signal having the first transmission wavelength transmittedby the subscriber device 40-2 is output to the electrical processingunit 600 via the optical SW 210. The O/E conversion unit 610 convertsthe transmission signal input from the optical SW 210 into an electricalsignal. In a case where it is determined that the determinationconditions included in the first instruction information are satisfiedwith reference to predetermined information included in the transmissionsignal converted into the electrical signal, the processing executionunit 620 performs transmission signal electrical processingcorresponding to the determination conditions on the transmissionsignal. For example, the processing execution unit 620 performs errorcorrection such as forward error correction (FEC). The E/O conversionunit 630 converts the transmission signal of the electrical signalsubjected to the error correction by the processing execution unit 620into an optical signal having the second transmission wavelengthindicated by the first instruction information, and outputs the opticalsignal to the optical SW 210. The optical SW 210 outputs thetransmission signal having the second transmission wavelength to thetransmission line 541 corresponding to the ground C. By performing errorcorrection, transmission characteristics are improved.

The optical SW 210 outputs the reception signal having the firstreception wavelength input from the transmission line 542 correspondingto the communication destination subscriber device 40 at the ground C tothe electrical processing unit 600. The O/E conversion unit 610 convertsthe reception signal input from the optical SW 210 into an electricalsignal. In a case where it is determined that the determinationconditions included in the second instruction information are satisfiedwith reference to predetermined information included in the transmissionsignal converted into the electrical signal, the processing executionunit 620 performs reception signal electrical processing correspondingto the determination conditions on the reception signal. The E/Oconversion unit 630 converts the reception signal of the electricalsignal subjected to the reception signal electrical processing by theprocessing execution unit 620 into an optical signal having the secondreception wavelength indicated by the second instruction information,and outputs the optical signal to the optical SW 210. The optical SW 210outputs the transmission signal having the second reception wavelengthto the transmission line 522 corresponding to the subscriber device40-2.

FIG. 59 is a diagram illustrating a configuration example of the opticalaccess system 116 in a case where the electrical processing unit 600multiplexes signals. The electrical processing unit 600 includes O/Econversion units 610-1 and 610-2 as a plurality of O/E conversion units610.

An uplink optical signal of the subscriber device 40-3 and an uplinkoptical signal of the subscriber device 40-M are input to the electricalprocessing unit 600 via the optical SW 210. The electrical processingunit 600 has an OLT function. The processing execution unit 620 of theelectrical processing unit 600 performs processing at an electricalstage of the OLT function. A plurality of subscriber devices 40 areconnected to an OLT. The processing execution unit 620 having the OLTfunction collectively manages the subscriber devices 40.

The O/E conversion unit 610-1 converts the uplink optical signal of thesubscriber device 40-3 input from the optical SW 210 into an electricalsignal and outputs the electrical signal to the processing executionunit 620. The O/E conversion unit 610-2 converts the uplink opticalsignal of the subscriber device 40-M input from the optical SW 210 intoan electrical signal and outputs the electrical signal to the processingexecution unit 620. The processing execution unit 620 combines theuplink electrical signals transmitted from the subscriber device 40-3and the subscriber device 40-M into one signal, and outputs the signalto the E/O conversion unit 630. The E/O conversion unit 630 converts theuplink electrical signal output from the processing execution unit 620into an optical signal according to a wavelength designated from thecontrol unit 230, and outputs the optical signal to the optical SW 210.The optical SW 210 outputs the uplink optical signal input from theelectrical processing unit 600 to the transmission line 541corresponding to the ground C. As described above, the electricalprocessing unit 600 receives each of a plurality of optical signalsdropped by the optical GW 2016 and converts the optical signal into anelectrical signal, multiplexes the signals related to the same targetground with the multiplexing circuit, converts the multiplexed signalinto an optical signal again, and transmits the optical signal to theoptical GW 2016. Consequently, a transmission rate can be maximized.FIGS. 58 and 59 illustrate an example in which one electrical processingunit is provided, but a plurality of electrical processing units may beprovided.

The power splitter 507 between the subscriber device 40 and the opticalGW 2016 may be a wavelength multiplexer/demultiplexer. For example, in acase where the optical access system 116 is a WDM-PON, a wavelengthdemultiplexer is used between the subscriber device 40 and the opticalGW 2016.

(Seventeenth Configuration Example of Optical Access System 100)

The present configuration example is a mode in which optical SWs atdifferent ground are connected in a ring form. Hereinafter, adescription will focus on differences from each of the aboveconfiguration examples.

FIG. 60 is a diagram illustrating a configuration example of an opticalaccess system 117. The optical access system 117 has a configuration inwhich optical SWs 212 at three or more different grounds are connectedin a ring form via the optical communication network 30. In the exampleillustrated in FIG. 60 , the optical access system 117 has aconfiguration in which an optical SW 212 a that is the optical SW 212 atthe ground A, an optical SW 212 b that is the optical SW 212 at theground B, and an optical SW 212 c that is the optical SW 212 at theground C are connected in a ring form. A path between the optical SW 212a and the optical SW 212 b in the optical communication network 30 willbe referred to as a path P31, a path between the optical SW 212 b andthe optical SW 212 c in the optical communication network 30 will bereferred to as a path P32, and a path between the optical SW 212 c andthe optical SW 212 a in the optical communication network 30 will bereferred to as a path P33. One or more subscriber devices 40 a areconnected to the optical SW 212 a, one or more subscriber devices 40 bare connected to the optical SW 212 b, and one or more subscriberdevices 40 c are connected to the optical SW 212 c.

As the optical SW 212, the above-described optical SW or optical GW isused. For example, the ground B in FIGS. 6 to 10, 38, and 43 to 59 isdefined as a counterclockwise ground in the ring illustrated in FIG. 60, and the ground C in FIGS. 6 to 10, 38, and 43 to 59 is defined as aclockwise ground in the ring illustrated in FIG. 60 . In this case, theoptical SW 212 a at the ground A is connected to the optical SW 212 b atthe ground B via the path P31, and the optical SW 212 b at the ground Bis connected to the optical SW 212 a at the ground A via the path P32,the optical SW 212-c at the ground C, and the path P33. The optical SW212 a at the ground A is connected to the optical SW 212 c at the groundC via the path P33, and the optical SW 212 c at the ground C isconnected to the optical SW 212 a at the ground A via the path P32, theoptical SW 212 b at the ground B, and the path P31.

Thus, with the counterclockwise connection from the optical SW 212 a atthe ground A to the optical SW 212 b at the ground B as a backup system,connection based on the clockwise path connecting the optical SW 212 aat the ground A to the optical SW 212 b at the ground B via the opticalSW 212 c at the ground C is also possible, and counterclockwiseconnection is also possible. Similarly, with clockwise connection fromthe optical SW 212 a at the ground A to the optical SW 212 c at theground C as a backup system, connection based on counterclockwise pathconnecting the optical SW 212-a at the ground A to the optical SW 212 cat the ground C via the optical SW 212 b at the ground B is alsopossible, and clockwise connection is also possible.

As a backup system of connection between the subscriber devices 40 aconnected to the optical SW 212 a at the ground A, a counterclockwisepath passing through the path P31, the optical SW 212 b at the ground B,the path P32, the optical SW 212 c at the ground C, and the path P33, ora counterclockwise path passing through the path P33, the optical SW 212c at the ground C, the path P32, the optical SW 212 b at the ground B,and the path P31 may be used.

For example, in FIG. 14 , the medium-distance line P2 may be acounterclockwise path of the ring, and the medium-distance line P3 maybe a clockwise path of the ring. Any one of the grounds #1 to #q inFIGS. 16 and 19 may be a counterclockwise ground of the ring, andanother may be a clockwise ground of the ring. In a case where FIGS. 27and 28 illustrate the optical SW 1010 in one GW, any one of the uplink#11 to the uplink #43 may be set as a counterclockwise path of the ring,and another may be set as a clockwise path of the ring. Here, a path notselected as the path of the ring may be a path of the ring similarly tothe path selected as the path of the ring, may be an oblique line otherthan the ring, may be connected to the subscriber device 40, or may beconnected to another optical SW 1010 illustrated in FIGS. 27 and 28 .

In the above description, as a basic configuration, when multicast isperformed, uplink or downlink multicast is realized via the returntransmission line as illustrated in FIG. 4 or 5 . For example, in theexample illustrated in FIG. 4 , in order to realize uplink multicast,the optical signal output from the port 11-2 of the optical SW 10 c isinput to the other port 11-2 via the return transmission line, and theoptical SW 10 c outputs the input optical signal to the port 11-1 towhich the 1×N power splitter 71 is connected. The optical signal outputfrom the port 11-1 is divided by the power splitter 71 and input to aplurality of other ports 11-1, and thus uplink multicast is realized.However, in such a configuration, since it is necessary to use a portfor return when multicast is performed, the number of ports in use mayincrease. Such a problem occurs not only in a case where multicastrouting is performed but also in a case where broadcast routing isperformed. Therefore, in the following embodiments, a configuration forreducing the number of ports when multicast or broadcast routing isperformed will be described. In the following description of theembodiments, the control unit 20 and the OPS 300 are not illustrated inthe drawings, but in the optical access system, wavelength setting andconnection setting of the optical SW by the control unit 20 or the OPS300 are performed.

First Embodiment

In the following embodiments including the present embodiment, uplinkmulticast from the subscriber device 40 a connected to the port 11-1 tothe subscriber device 40 b or 40 c connected to the port 11-2 or anuplink will be mainly described. However, if the port 11-1 and the port11-2 are interchanged in line symmetry in the center optical SW 210, anuplink or multicast from the subscriber device 40 b or 40 c connected tothe port 11-2 to the subscriber device 40 a connected to the port 11-1or the like is performed. Also in broadcast, a flow of processing issimilar to that in multicast.

FIG. 61 is a diagram illustrating a configuration example of an opticalGW 200 a in the optical access system of the first embodiment. In FIG.61 , a case of multicasting uplink optical signals transmitted from thesubscriber devices 40 a-1 and 40 a-2 located at the ground A will bedescribed. Here, in the description, as illustrated in FIG. 61 , it isassumed that ports connected by a dotted line are connected inside theoptical SW 210 a. This connection between the ports is executed by theoptical SW controller 320 (not illustrated).

The optical GW 200 a returns an optical signal output from the port 11-2without using the optical SW 210 a-1, and inputs the optical signal tothe power splitter 71 connected to the port 11-1. This enablesmulticast. FIG. 61 illustrates two configurations, that is, aconfiguration in which the optical signal passes through another opticalswitch and a configuration in which the optical signal does not passthrough another optical switch when the optical signal is returnedwithout passing through the optical SW 210 a-1. Hereinafter, eachconfiguration will be described.

(Configuration in which Signal does not Pass Through Another OpticalSwitch)

In the configuration in which a signal does not pass through anotheroptical switch, the optical GW 200 a includes an optical SW 210 a-1, atransmission line 2101, and a power splitter 71-1. The transmission line2101 connects a port (for example, the port 11-2-1) on the output sideof the optical SW 210 a-1 and the power splitter 71-1 via the outside ofthe optical SW 210 a-1. The connection via the outside of the optical SW210 a-1 means that a signal does not pass through the inside (betweenports) of the optical SW 210 a-1. That is, the transmission line 2101 isa transmission line that is provided outside the optical SW 210 a-1 anddirectly connects the port 11-2-1 and the power splitter 71-1. Thetransmission line 2101 is, for example, an optical fiber. The powersplitter 71-1 divides the input optical signal into a plurality ofoptical signals, and inputs the plurality of divided optical signals todifferent ports 11-1. A new power splitter may be provided between thepower splitter 71-1 and the port 11-1. In this case, the power splitter71-1 divides the input optical signal into a plurality of opticalsignals, and inputs some or all of the plurality of divided opticalsignals to the port 11-1 via the power splitter.

A flow of processing in a case where the optical GW 200 a has theconfiguration in which a signal does not pass through another opticalswitch will be described. In FIG. 61 , the optical GW 200 a outputs,from the port 11-2-1, an optical signal transmitted by the subscriberdevice 40 a-1 and input to the port 11-1-1. The optical signal outputfrom the port 11-2-1 is input to the power splitter 71-1 connected tothe plurality of ports 11-1-n to 11-1-(n+2) via the transmission line2101. For example, in FIG. 61 , the power splitter 71-1 is connected tothe ports 11-1-3 to 11-1-5.

The power splitter 71 divides the input optical signal and inputs thedivided optical signals to the plurality of ports 11-1-3 to 11-1-5. Theoptical SW 210 a-1 outputs the optical signals input from the pluralityof ports 11-1-3 to 11-1-5 to different ports 11-2-3 to 11-2-5,respectively. Bidirectional communication may also be performed. Theoptical signal in the downlink direction is routed in a reversedirection to the uplink direction.

In this case, the uplink direction is related to one-to-manycommunication, and the downlink direction is related to many-to-onecommunication. In this case, the power splitter 71 is used as acombining/branching device. The power splitter 71 used here has H×Iinput/output ports. H and I are integers of 1 or more, and H≤I. In thecase of H=1 and I=2, the power splitter 71, for example, branches anoptical signal in the uplink direction and multiplexes optical signalsin the downlink direction. In the example in FIG. 61 , the powersplitter 71 branches the input optical signal, inputs the branchedoptical signals to the plurality of ports 11-1-3 to 11-1-5, multiplexesoptical signals respectively output from the plurality of ports 11-1-3to 11-1-5, and outputs the multiplexed optical signal to thetransmission line 2101.

In order to realize the above processing, in a case where a multicasttransmission request is made from the subscriber device 40 a-1, theoptical SW controller 320 connects the port 11-1-1 to which thesubscriber device 40 a-1 is connected and the port 11-2-1 to which thepower splitter 71-1 for performing multicast is connected. Consequently,the optical signal transmitted from the subscriber device 40 a-1 isoutput from the port 11-2-1. The optical SW controller 320 connects theports 11-1-3 to 11-1-5 to which the power splitter 71-1 is connected andthe port 11-2 (in FIG. 61, 11-2-3 to 11-2-5 ) corresponding to thetransfer destination on the path to the communication destination.Consequently, each optical signal branched by the power splitter 71-1 isoutput from the port 11-2 to which the destination subscriber device 40b is connected. With such a configuration, the optical signal isreturned to enable multicast.

In the case of downlink multicast, the following applies.

The optical GW 200 a includes an optical SW 210 a-1, a transmissionline, and a power splitter. The transmission line connects a port (forexample, the port 11-1-1) on the output side of the optical SW 210 a-1and the power splitter via the outside of the optical SW 210 a-1. Thetransmission line is a transmission line that directly connects the port11-1-1 and the power splitter. The transmission line is, for example, anoptical fiber. The power splitter divides an input optical signal into aplurality of optical signals, and inputs the plurality of dividedoptical signals to different ports 11-2. The optical SW 210 a-1 outputsthe optical signal input to the port 11-2-1 from the port 11-1-1. Theoptical signal output from the port 11-1-1 is input to the powersplitter connected to the plurality of ports 11-2-n to 11-2-(n+2) viathe transmission line. For example, the power splitter is connected tothe ports 11-2-3 to 11-2-5.

The power splitter divides the input optical signal and inputs thedivided optical signals to the plurality of ports 11-2-3 to 11-2-5. Theoptical SW 210 a-1 outputs the optical signals input from the pluralityof ports 11-2-3 to 11-2-5 to the different ports 11-1-3 to 11-1-5,respectively.

(Configuration in which Signal Passes Through Another Optical Switch)

In the configuration in which a signal passes through another opticalswitch, the optical GW 200 a includes an optical SW 210 a-1, an opticalSW 210 a-2, a transmission line 2102, and a power splitter 71-2. Theoptical SW 210 a-2 is connected to a port (for example, the port 11-2-q)on the output side of the optical SW 210 a-1. The transmission line 2102connects the optical SW 210 a-2 and the power splitter 71-2 via theoutside of the optical SW 210 a-1. The optical SW 210 a-2 outputs anoptical signal output from the port 11-2 on the output side of theoptical SW 210 a-1 to the power splitter 71-2 via the transmission line2102. The power splitter 71-2 divides the input optical signal into aplurality of optical signals, and inputs the plurality of dividedoptical signals to different ports 11-1. A new power splitter may beprovided between the power splitter 71-2 and the port 11-1. In thiscase, the power splitter 71-1 divides the input optical signal into aplurality of optical signals, and inputs some or all of the plurality ofdivided optical signals to the port 11-1 via the power splitter. Theoptical GW 200 a may have only one or both of a configuration in which asignal does not pass through another optical switch and a configurationin which a signal passes through another optical switch.

A flow of processing in a case where the optical GW 200 a has theconfiguration in which a signal passes through another optical switchwill be described. In FIG. 61 , the optical GW 200 a outputs an opticalsignal transmitted by the subscriber device 40 a-2 and input to the port11-1-p from the port 11-2-q. The optical signal output from the port11-2-1 is input to the optical SW 210 a-2. The optical SW 210 a-2outputs the optical signal output from the port 11-2-q to the powersplitter 71-2 connected to the plurality of ports 11-1-(P−2) to 11-1-Pvia the transmission line 2102.

The power splitter 72 divides the input optical signal and inputs thedivided optical signals to the plurality of ports 11-1-(P−2) to 11-1-P.The optical SW 210 a-1 outputs the optical signals input from theplurality of ports 11-1-(P−2) to 11-1-P to different ports 11-1-(Q−2) to11-1-Q, respectively. Bidirectional communication may also be performed.The optical signal in the downlink direction is routed in a reversedirection to the uplink direction. In this case, the uplink direction isrelated to one-to-many communication, and the downlink direction isrelated to many-to-one communication. In this case, the power splitter71 is used as a combining/branching device. The power splitter 71 usedhere has H×I input/output ports. In the case of H=1 and I=2, the powersplitter 71, for example, branches an optical signal in the uplinkdirection and multiplexes optical signals in the downlink direction. Inthe example in FIG. 61 , the power splitter 71 branches the inputoptical signal, inputs the branched optical signals to the plurality ofports 11-1-(Q−2) to 11-1-Q, multiplexes the optical signals output fromthe plurality of ports 11-1-(Q−2) to 11-1-Q, and outputs the multiplexedoptical signal to the transmission line 2102.

In order to realize the above processing, in a case where a multicasttransmission request is made from the subscriber device 40 a-2, theoptical SW controller 320 connects the port 11-1-p to which thesubscriber device 40 a-2 is connected and the port 11-2-q to which thepower splitter 71-2 for performing multicast is connected. Consequently,the optical signal transmitted from the subscriber device 40 a-2 isoutput from the port 11-2-q. The optical SW controller 320 connects theports 11-1-(P−2) to 11-1-P to which the power splitter 71-2 is connectedand the port 11-2 (in FIG. 61, 11-2 -(Q−2) to 11-2-Q) corresponding tothe transfer destination on the path to the communication destination.Consequently, each optical signal branched by the power splitter 71-2 isoutput from the port 11-2 to which the destination subscriber device 40c is connected. With such a configuration, the optical signal isreturned to enable multicast to the destination.

In the case of downlink multicast, the following applies.

The optical GW 200 a includes an optical SW 210 a-1, an optical SW 210a-2, a transmission line, and a power splitter. The optical SW 210 a-2is connected to a port (for example, port 11-1-q) on the output side ofthe optical SW 210 a-1. The transmission line connects the optical SW210 a-2 and the power splitter via the outside of the optical SW 210a-1. The optical SW 210 a-2 outputs an optical signal output from theport on the output side of the optical SW 210 a-1 to the power splittervia the transmission line. The power splitter divides an input opticalsignal into a plurality of optical signals, and inputs the plurality ofdivided optical signals to different ports 11-2. The optical GW 200 amay have only one or both of a configuration in which a signal does notpass through another optical switch and a configuration in which asignal passes through another optical switch.

According to the optical GW 200 a configured as described above, theport of the optical SW 210 a-1 is not used as a return path whenmulticast or broadcast routing is performed. Therefore, even in a casewhere routing is performed, the number of paths inside the optical SW210 a-1 is reduced by one path, that is, one port for each of the ports11-1-p and 11-2-q. Therefore, it is possible to transmit an opticalsignal according to a transfer destination on a path to a communicationdestination while reducing the number of use ports when multicast orbroadcast routing is performed in the optical SW 210 a-1.

In the first embodiment, a power splitter is mainly used, but amultiplexer/demultiplexer may be used in a case of performing multicastin which a signal is demultiplexed for each wavelength (effectively,unicast in which a signal is demultiplexed according to wavelengths).

Second Embodiment

In the first embodiment, the configuration in which an optical signaloutput from the port 11-2 once via the optical SW is returned via theoutside of the optical SW has been described. In this case, in order toreturn the optical signal, it is necessary to transmit the opticalsignal between the ports of the optical SW once, and thus thecorresponding number of ports cannot be used. Therefore, in the secondembodiment, a configuration for reducing the number of ports whenmulticasting is performed compared with the first embodiment will bedescribed. Also in broadcast, a flow of processing is similar to that inmulticast.

FIG. 62 is a diagram illustrating a configuration example of an opticalGW 200 b in the optical access system of the second embodiment. In FIG.62 , a case of multicasting uplink optical signals transmitted from thesubscriber devices 40 a-1 and 40 a-2 located at the ground A will bedescribed. Here, in the description, as illustrated in FIG. 62 , it isassumed that ports connected by a dotted line are connected inside theoptical SW 210 b. This connection between the ports is executed by theoptical SW controller 320 (not illustrated).

The optical GW 200 b divides an optical signal output from thesubscriber device 40 a-1 into a plurality of optical signals, and inputsthe plurality of divided optical signals to different ports 11-1.Consequently, multicast can be performed by reducing one set of portsfor returning an optical signal. The optical GW 200 b includes powersplitters 71-1 and 71-2. The optical GW 200 b may include either thepower splitter 71-1 or the power splitter 71-2, or may include both.

In FIG. 62 , the power splitter 71-1 divides an optical signal outputfrom the subscriber device 40 a-1 into a plurality of optical signals,and inputs the plurality of divided optical signals to different ports11-1 (in FIG. 62 , the ports 11-1-3 to 11-1-5). The power splitter 71-1is connected to the subscriber device 40 a-1 via the transmission line2103. The power splitter 71-2 divides the optical signal output from thesubscriber device 40 a-2 into a plurality of optical signals, and inputsthe plurality of divided optical signals to different ports 11-1 (inFIG. 62, 11-1 -(P−2) to 11-1-P). The power splitter 71-2 is connected tothe subscriber device 40 a-2 via the transmission line 2104. New powersplitters may be provided between the power splitter 71-1 and the port11-1 and between the power splitter 71-2 and the port 11-1. In thiscase, each of the power splitters 71-1 and 71-2 divides an input opticalsignal into a plurality of optical signals, and inputs some or all ofthe plurality of divided optical signals to the ports 11-1 via the powersplitter.

As described above, in the second embodiment, the power splitter 71 orthe power splitter 72 is provided at the preceding stage with respect toinputting the optical signal to the port 11-1, and the optical signaloutput from the subscriber device 40 a is multicasted. The optical SW210 b outputs the optical signals input from the plurality of ports 11-1to different ports 11-2, respectively. Bidirectional communication mayalso be performed. The optical signal in the downlink direction isrouted in a reverse direction to the uplink direction. In this case, thepower splitter 71 is used as a combining/branching device. The powersplitter 71 used here has H×I input/output ports. In the case of H=1 andI=2, the power splitter 71, for example, branches an optical signal inthe uplink direction and multiplexes optical signals in the downlinkdirection. In the example in FIG. 62 , the power splitter 71 branchesthe input optical signal, inputs the branched optical signals to theplurality of ports 11-1-3 to 11-1-5, multiplexes the optical signalsrespectively output from the plurality of ports 11-1-3 to 11-1-5, andoutputs the multiplexed optical signal to the subscriber device 40 a-1.

In order to realize the above processing, in a case where a multicasttransmission request is made from the subscriber device 40 a, theoptical SW controller 320 connects the port 11-1 to which the powersplitter 71 to which the subscriber device 40 a that is a transmissionsource of the transmission request is connected is connected and theport 11-2 corresponding to the transfer destination on the path to thecommunication destination. Consequently, the optical signal transmittedfrom the subscriber device 40 a is branched into a plurality of opticalsignals by the power splitter 71, and each of the plurality of branchedoptical signals is output from port 11-2 that is a transfer destinationon the path to the communication destination. Such a configurationenables multicast to a destination while reducing the number of ports.

According to the optical GW 200 b configured as described above, thereturn path as described in the basic configuration or the firstembodiment is not used to perform multicast. Therefore, the number ofports used for the return path can be reduced. For example, in thesecond embodiment, compared with the first embodiment, the number ofpaths inside the optical SW 210 b is further reduced by one path, thatis, by one port of each of the ports 11-1-p and 11-2-q. Thus, it ispossible to transmit an optical signal according to a transferdestination on a path to a communication destination while reducing thenumber of ports to be used in the optical SW 210 b.

In the second embodiment, a power splitter is mainly used, but amultiplexer/demultiplexer may be used in a case of performing multicastin which a signal is demultiplexed for each wavelength (effectively,unicast in which a signal is demultiplexed according to wavelengths).

Third Embodiment

In the second embodiment, although the number of ports can be reduced,when the subscriber device 40 a is connected, it is necessary to selectwhether to connect the subscriber device 40 a to the power splitter orto connect the subscriber device 40 a to a port not connected to thepower splitter. As described above, in the second embodiment, in a casewhere a communication source starts or stops multicast, a port to beconnected is changed. In the third embodiment, a configuration forsuppressing a port change will be described. In such a configuration,the above-described optical SW is replaced with a set ofcascade-connected optical SWs.

FIG. 63 is a diagram illustrating a configuration example of an opticalGW 200 c in the optical access system of the third embodiment. In FIG.63 , for simplification of description, an optical SW having a(11-1-P)×(11-2-Q) configuration will be described as a symmetric SW ofS×S or the like (where S is an integer of 1 or more), but the optical SWcan be easily expanded even in a case of an asymmetric optical SW suchas a SW having the (11-1-P)×(11-2-Q) configuration.

The optical GW 200 c illustrated in FIG. 63 includes a first opticalswitch 210 c-1, a second optical switch 210 c-2, and power splitters450-1 to 450-M. The first optical switch 210 c-1 and the second opticalswitch 210 c-2 are cascade-connected. In the cascade configuration ofthe optical GW 200 c in the third embodiment, the first optical switch210 c-1 of S×S and the second optical switch 210 c-2 of((S−T)+T×k)×((S−T)+T×k) are used. Here, S is the number of subscriberdevices 40 a, T is the number of ports to be branched, and k is thenumber of branches for each port. The number of ports to be branched isthe number of ports to which a power splitter is connected.

In a case where the number of branches k is different for each port, T×kis replaced with a sum of the number of branches of the port. Outputscorresponding to the branched T ports in the optical SW 210 c-1 of S×Sare connected to ports of the optical SW 210 c-2 of((S−T)+T×k)×((S−T)+T×k)) via the power splitters 450-1 to 450-M, andoutputs corresponding to the remaining (S-T) ports are directlyconnected to ports thereof.

Effects achieved by the third embodiment will be described.

The SW sizes of the two optical SWs illustrated in FIG. 63 are S² forthe first stage and ((S−T)+T×k)²=(S+T×(k−1))² for the second stage.Therefore, the maximum size (S+T×k)² decreases to (S+T× (k−1))², and atotal number of SW fabrics does not decrease at (S+T×k)²−{(S)²+[(S+T×(k−1))²]=S(2S−2k+1)−S².

Although all the ports are connected, there may be a free port or a portconnected to an electrical processing unit or the like. Here, aconfiguration in a case where the electrical processing unit or the likeis connected in the third embodiment will be described. In the opticalGW 200 c, the electrical processing unit is connected via an optical SW(for example, the optical switch 210 c-1) near the subscriber device 40a before a signal is multicasted or in a case where a signal passesthrough the optical SW without being multicasted, and the electricalprocessing unit is connected via another optical SW (for example, theoptical switch 210 c-2) in a case where a signal passes through eachoptical SW after being multicasted. It is preferable to pass throughbefore multicast in a case where forward error correction (FEC),encryption, or the like is collectively processed, and it is preferableto pass through after multicast in a case where FEC, encryption, or thelike is changed for each destination.

In the third embodiment, bidirectional communication is also possible.The optical signal in the downlink direction is routed in a reversedirection to the uplink direction. In this case, the power splitter 450is used as a combining/branching device. The power splitter 450 usedhere has H×I input/output ports. In the case of H=1 and I=2, the powersplitter 450, for example, branches an uplink optical signal andmultiplexes downlink optical signals. In the example in FIG. 63 , thepower splitter 450 branches an input optical signal, inputs the branchedoptical signals to a plurality of ports of the optical SW 210 c-2,multiplexes optical signals respectively output from the plurality ofports of the optical SW 210 c-2, and outputs the multiplexed opticalsignal to the port 11-2 (for example, the port 11-2-(Q−1)) of theoptical SW 210 c-1.

Fourth Embodiment

FIG. 64 is a diagram illustrating a configuration example of an opticalGW 200 d in the optical access system of the third embodiment. In FIG.64 , for simplification of description, an optical SW having a(11-1-P)×(11-2-Q) configuration will be described as a symmetric SW ofS×S or the like, but the optical SW can be easily expanded even in acase of an asymmetric optical SW such as a SW having the(11-1-P)×(11-2-Q) configuration.

The optical GW 200 d illustrated in FIG. 64 includes a first opticalswitch 210 c-1, a second optical switch 210 d-2, and power splitters450-1 to 450-M. The optical GW 200 d is different from the optical GW200 c in that the second optical switch 210 d-2 is provided instead ofthe second optical switch 210 c-2. In the cascade configuration of theoptical GW 200 d in the fourth embodiment, an optical SW of S×S and anoptical SW of (T×k)×(T×k) are used.

In a case where the number of branches k is different for each port, T×kis replaced with a sum of the number of branches of the port. Outputscorresponding to branched T ports in the optical SW 210 c-1 of S×S areconnected to the second optical switch 210 d-2 via the power splitters450-1 to 450-M. Outputs corresponding to the remaining (S−T) ports donot pass through the second optical switch 210 d-2.

Effects achieved by the fourth embodiment will be described.

The SW sizes of the two optical SWs illustrated in FIG. 64 are S² forthe first stage and (T×k)² for the second stage. Therefore, the maximumsize (S+T×k)² decreases to MAX(S², (T×k)²), and a total number of SWfabrics decreases by (S+T×k)²−{(S)²+(T×k)²}=2STk.

Although all the ports are connected, there may be a free port or a portconnected to an electrical processing unit or the like. Here, aconfiguration in a case where the electrical processing unit or the likeis connected in the fourth embodiment will be described. In the opticalGW 200 d, the electrical processing unit is connected via an optical SW(for example, the optical switch 210 c-1) near the subscriber device 40a before a signal is multicasted or in a case where a signal passesthrough the optical SW without being multicasted, and the electricalprocessing unit is connected via another optical SW (for example, theoptical switch 210 d-2) in a case where a signal passes through eachoptical SW after being multicasted. It is preferable to pass throughbefore multicast in a case where forward error correction (FEC),encryption, or the like is collectively processed, and it is preferableto pass through after multicast in a case where FEC, encryption, or thelike is changed for each destination.

In the fourth embodiment, bidirectional communication is also possible.The optical signal in the downlink direction is routed in a reversedirection to the uplink direction. In this case, the power splitter 450is used as a combining/branching device. The power splitter 450 usedhere has H×I input/output ports. In the case of H=1 and I=2, the powersplitter 450, for example, branches an uplink optical signal andmultiplexes downlink optical signals. In the example in FIG. 64 , thepower splitter 450 branches an input optical signal, inputs the branchedoptical signals to a plurality of ports of the optical SW 210 d-2,multiplexes optical signals respectively output from the plurality ofports of the optical SW 210 d-2, and outputs the multiplexed opticalsignal to the port 11-2 (for example, the port 11-2-(Q−1)) of theoptical SW 210 c-1.

Fifth Embodiment

In the basic configuration, as illustrated in FIGS. 3 to 5 , theconfiguration in which the power splitter or the WDM device is notprovided in the return transmission line, and the ports are directlyconnected to each other to return an optical signal has been described.In the fifth embodiment, a variation of a configuration of returning anoptical signal will be described. For example, a return transmissionline may be configured by a network that is returned via a network of anoptical SW or the like in an intermediate layer, such as a folded Closnetwork. The return transmission line may be configured such that someports of some input/output SWs of the folded Clos network to anintermediate layer SW and some ports of the intermediate layer SW aredisposed on 11-2-Q side, and some of the ports of some input/output SWsto the intermediate layer SW and some of the ports of the intermediatelayer SW are disposed on 11-2-Q side. Consequently, the optical SWenables return communication.

FIG. 65 is a diagram illustrating a configuration example of an opticalGW 200 e in the optical access system of the fifth embodiment. In FIG.65 , three configurations (first to third configurations) will bedescribed as variations of the configuration of returning an opticalsignal.

(First Configuration of Returning Optical Signal)

In the first configuration of returning an optical signal, the opticalGW 200 e includes an optical SW 210 e-1 and a WDM device 80-1. Thesubscriber devices 40 a-1 and 40 a-2 are connected to the ports 11-1-1and 11-1-2 of the optical GW 200 e via transmission lines 50-1-1 and50-1-2. The WDM device 80-1 is connected to the ports 11-2-1 and 11-2-2of the optical GW 200 e. The subscriber devices 40 a-1 and 40 a-2transmit and receive optical signals having different wavelengths. TheWDM device 80-1 multiplexes optical signals respectively output from theports 11-2-1 and 11-2-2 and outputs the multiplexed optical signal to areturn transmission line 51 a-1. The return transmission line 51 a-1 isconnected to the port 11-2-3. With such a configuration, an opticalsignal can be returned.

(Second Configuration of Returning Optical Signal)

In the second configuration of returning an optical signal, the opticalGW 200 e includes an optical SW 210 e-1, a plurality of WDM devices 80-2and 80-3, and a plurality of monitoring units 60-1 and 60-2. Thesubscriber devices 40 a-p and 40 a-(p+1) are connected to the ports11-1-p and 11-1-(p+1) of the optical GW 200 e via transmission lines50-1-p and 50-1-(p+1). The WDM device 80-2 is connected to the ports11-2-q and 11-2-(q+1) of the optical GW 200 e.

The subscriber devices 40 a-p and 40 a-(p+1) transmit and receiveoptical signals having different wavelengths. The WDM device 80-2multiplexes optical signals respectively output from the ports 11-2-1and 11-2-2 and outputs the multiplexed optical signal to a returntransmission line 51 a-2. The return transmission line 51 a-2 isconnected to the WDM device 80-3. The WDM device 80-3 demultiplexes theinput optical signal and outputs the demultiplexed optical signals tothe monitoring units 60-1 and 60-2, respectively. The monitoring units60-1 and 60-2 monitor optical signals transmitted through thetransmission lines. With such a configuration, an optical signal can bereturned.

(Third Configuration of Returning Optical Signal)

In the third configuration of returning an optical signal, the opticalGW 200 e includes an optical SW 210 e-1 and an optical SW 210 e-2. Thesubscriber device 40 a-P is connected to the port 11-1-(P−1) of theoptical GW 200 e via a transmission line 50-1-P. The optical SW 210 e-2is connected to the port 11-2-(Q−1) of the optical GW 200 e. Thesubscriber devices 40 a-P transmit and receive optical signals. Theoptical SW 210 e-1 outputs an optical signal input from the port11-1-(P−1) from the port 11-2-(Q−1). The optical signal output from theport 11-2-(Q−1) is output to the optical SW 210 e-2. The optical SW 210e-2 outputs the input optical signal to the port 11-2-Q. With such aconfiguration, an optical signal can be returned.

According to the optical GW 200 e configured as described above, aconfiguration for return communication other than the configurationillustrated in the basic configuration can be applied. Consequently, thedegree of freedom of combination is improved, and convenience can beimproved.

Next, a configuration for reducing the number of ports to be used of anoptical SW accommodating the subscriber device 40 will be presented.Here, the optical SW 1010 illustrated in FIGS. 27 and 28 will bedescribed as an example, but the optical SW can be similarly applied toother optical SWs (for example, the optical SW 10 and the optical SW210) described above.

In the configuration illustrated in FIGS. 27 and 28 , for example, whenviewed from the subscriber device 40 (in FIGS. 27 and 28 , the ONU) onthe port 11-1 side as a transmission line, it clearly corresponds to anincrease in the number of connections of output paths connected to theport 11-2. Therefore, in a case where the optical SW 1010 is connectedto the subscriber device 40 on the port 11-1 side of another optical SW1010 (for example, optical SW 1010-2 to 1010-4) as described above andthe optical SW 1010 is connected in the full mesh type as illustrated inFIG. 27 , six ports are occupied with the port 11-1 (for example, theport 11-1-1 (connected to the ONU #11)) and the port 11-2 (for example,the port 11-2-q 1 (connected to *a)) of the optical SW 1010-1, the port11-1 and the port 11-2 (for example, the port 11-1-p 1 (connected to *a)and the port 11-2-x (connected to the return transmission line) of theoptical SW 1010-2 to which the opposing subscriber device 40 isconnected on the port 11-1 side, the port 11-2 and the port 11-2 (forexample, the port 11-2-y and the port 11-2-z) connected to and thereturn transmission line, and the port 11-1 (for example, the port11-1-1 (connected to the ONU #21)) to which the opposing ONU isconnected. The same applies to a case where a return transmission lineis provided in the optical SW 1001.

In the case of being connected in the ring form as illustrated in FIG.28 , eight ports are occupied with the port 11-1 and the port 11-2 (forexample, the port 11-1-1 (connected to ONU #11) and port 11-2-q 1(connected to *a)) of the optical SW 1010-1, the port 11-1 and the port11-2 (for example, the port 11-1-p 1 (connected to *a) and the port11-2-q 1 (connected to *d)) of the intermediate optical SW 1010-2, theport 11-1 and the port 11-2 (for example, the port 11-1-p 1 (connectedto *d) and the port 11-2-x (connected to the return transmission line)of the optical SW 1010-3 to which the opposing subscriber device 40 isconnected on the port 11-1 side, the port 11-2 and the port 11-2 (forexample, port 11-2-y, port 11-2-z) connected to the return transmissionline, and the port 11-1 (for example, the port 11-1-1 (connected to theONU #21) to which the opposing ONU is connected. The same applies to acase where a return transmission line is provided in the optical SW1010-1 or the optical SW 1010-2.

In view of the above, a configuration for reducing the number of portsto be used of an optical SW accommodating the subscriber device 40 willbe described with reference to FIG. 66 . In FIG. 66 , fourconfigurations are illustrated as configurations for reducing the numberof ports to be used of the optical SW.

(First Configuration)

As illustrated in FIG. 66(A), in a first configuration, the optical SW1010-1 to the optical SW 1010-3 and the optical SW 1200 are illustrated.In the first configuration, from the viewpoint of improving the degreeof freedom of connection for changing a ratio of ports of an optical SWdelivered to a transmission line crossing the optical SW, thetransmission line crossing the optical SW is the optical SW 1200. Aconfiguration of the optical SW 1200 is basically similar to that of theother optical SWs 1010. In a case where the transmission line crossingthe optical SW is the optical SW, the number of ports to be used of theoptical SW accommodating the subscriber device 40 can be reduced.

Means for reducing the number of ports to be used of the optical SWaccommodating the subscriber device 40 will be described. In FIG. 27 ,crossing transmission lines connected to each of the optical SWs 1010-1to 1010-4 are illustrated as one set, but the crossing transmissionlines are occupied from a single optical SW 1010 and connected to an ONUof the same optical SW. For example, in the example in FIG. 27 , in acase where the ONU #11, the ONU #12, and the ONU #13 are connected tothe ONU #21, the ONU #22, and the ONU #23, 22 ports including, forexample, 6 ports, 8 ports, and 8 ports are occupied via another opticalSW. In contrast, as illustrated in FIG. 66 (A), in a case where thetransmission line crossing the optical SW is the optical SW 1200, 18ports are sufficient as ports of the optical SW 1010-1 and the opticalSW 1010-2 that accommodate the subscriber device 40. The optical SWs1010-1 to 1010-4 are an aspect of a plurality of optical switches. Inthis description, the optical SW 1010-1 will be described as an aspectof a first optical switch among the plurality of optical switches, andthe optical SW 1010-2 will be described as an aspect of a second opticalswitch among the plurality of optical switches.

More specifically, the optical SW 1200 is connected to the port 11-1 andthe port 11-2 of the optical SW 1010-1, and is further connected to theport 11-1 and the port 11-2 of the optical SW 1010-2 and the port 11-1and the port 11-2 of the optical SW 1010-3. In the above-described way,the optical SW 1200 is connected to the first ports (for example, theports 11-1) of the plurality of optical switches and the second ports(for example, the ports 11-2) on the side (for example, the sidedifferent from the side on which the port 11-1 is provided in theplurality of optical switches) different from the first ports. The firstport and the second port illustrated here are examples, and the port11-1 may be the second port and the port 11-2 may be the first port. Thesame applies to the following description. The optical SW 1200 connectsthe ports 11-2 on the output side of the plurality of optical SWs 1010and the ports 11-1 on the input side of the plurality of optical SWs1010. For example, the optical SW 1200 connects the port 11-2 on theoutput side of the optical SW 1010-1 and the port 11-1 on the input sideof the optical SW 1010-2. The optical SW controller 320 controls theoptical SW 1200 such that a path inside the optical SW 1200 becomes apath toward a transfer destination on a path to a communicationdestination. With such a configuration, as illustrated in FIG. 27 , thenumber of ports via other optical SWs 1010-2 and 1010-3 can be reduced.

(Second Configuration)

As illustrated in FIG. 66(B), in a second configuration, the optical SW1010-1 to the optical SW 1010-3 are illustrated. In the secondconfiguration, the return transmission line is not connected to the sameoptical SW, but is connected between the optical SWs connected via therespective opposing subscribers. For example, the connection is madesuch as by using the port 11-1-1 that connects the optical SW 1010-1 andthe ONU #11, the port 11-2-x of the optical SW 1010-1, the returntransmission line, the port 11-2-y of the optical SW 1010-2, and theport 11-1-1 that connects the optical SW 1010-2 and the ONU #21. Thatis, in the second embodiment, the ports 11-2 on the same side of thedifferent optical SWs 1010 are connected via the return transmissionline. In the example illustrated in FIG. 66(B), the port 11-2 of theoptical SW 1010-1 and the port 11-2 of the optical SW 1010-2 areconnected via the return transmission line, the port 11-2 of the opticalSW 1010-2 and the port 11-2 of the optical SW 1010-3 are connected viathe return transmission line, and the port 11-2 of the optical SW 1010-1and the port 11-2 of the optical SW 1010-3 are connected via the returntransmission line. In this case, since four ports are used, it can beseen that the number of ports to be used can be reduced by two portscompared with use of six ports.

(Third Configuration)

As illustrated in FIG. 66(C), in a third configuration, the optical SW1010-1 to the optical SW 1010-3 and the optical SW 1200 are illustrated.In the third configuration, the optical SW 1200 is used as a returntransmission line. In a case where the optical SW 1200 is a SW havingthe (11-1-P)×(11-2-Q) configuration, a single optical SW (for example,the optical SW 1010-1) accommodating the subscriber device 40 isconnected to each of the port 11-1 and the port 11-2 of the optical SW1200 that is a transmission line crossing the optical SW, and isconnected from the port 11-1 to the port 11-2 and from the port 11-2 tothe port 11-1. In a case where different optical SWs accommodating thesubscriber device 40 are connected to each other, a transmission linecrossing the optical SW is formed, and in a case where connection ismade through the same optical SW, a return transmission line in the sameSW is formed. That is, in the third configuration, some of the ports11-2 on the output side of the optical SW 1010-1 to the optical SW1010-3 are connected to the port 11-1 of the optical SW 1200, and theother of the ports 11-2 on the output side of the optical SW 1010-1 tothe optical SW 1010-3 are connected to the port 11-2 of the optical SW1200. Consequently, the optical SW 1200 connects the ports 11-2 on theoutput side of the optical SW 1010-1 to the optical SW 1010-3. Theoptical SW controller 320 controls the optical SW 1200 such that thepath inside the optical SW 1200 connects the ports 11-2 on the outputside of the optical SW 1010-1 to the optical SW 1010-3.

The second or third configuration may be combined with the transmissionline crossing the mesh type optical SW in FIG. 27 or the ring typeoptical SW in FIG. 28 or the first configuration.

(Fourth Configuration)

As illustrated in FIG. 66(D), in a fourth configuration, the optical SW1010-1 to the optical SW 1010-3 and the optical SW 1200 are illustrated.The fourth configuration is an extension of the third configuration. Inthe third configuration, at least some uplinks are installed on the port11-1 side rather than on the port 11-2 side, and, when ports areconnected to the uplinks, the ports are connected via a returntransmission line. That is, in the fourth configuration, the ports 11-1of the optical switches 1010-1 to 1010-3 that are not connected to theoptical SW 1200 are connected to the uplinks. This configuration issuitable in a case where return is mainly performed. For example, in acase where the subscriber devices 40 are connected to each other in afull mesh or a form close to a full mesh, the number of the ports 11-1is smaller than the number of the ports 11-2. In such a case, in a casewhere the optical SW is a symmetric SW of P×P, since the port 11-1 sideto which the subscriber is connected is left, the optical SW is divertedto the uplink side and the port is effectively utilized.

Next, as another aspect (modification example) of the monitoring unit 60illustrated in FIGS. 33 to 36 , a configuration in which the monitoringunit includes a transmitter will be specifically described withreference to FIGS. 67 to 69 . FIGS. 67 to 69 are configuration diagramsof another aspect (modification example) of the monitoring unit 60.Although the monitoring unit 60 will be described as an example in FIGS.67 to 69 , the monitoring unit 260 may be used instead of the monitoringunit 60, and a configuration of the monitoring unit 260 may be theconfiguration illustrated in FIGS. 67 to 69 . FIGS. 67 and 68 illustratean example in which a transmitter and a receiver are connected to atransmission line on the same side in opposite directions as aconfiguration for transmitting a signal toward a monitoring target. FIG.69 illustrates a configuration in which a transmitter and a receiver areconnected in the same direction in a case of merging into a transmissionline on an opposite side to the input of a main signal in the samedirection as the main signal.

A monitoring unit 75 a illustrated in FIG. 67(A) includes a powersplitter 61, a receiver 62, and a transmitter 76. The monitoring unit 75a illustrated in FIG. 67(A) is different from the monitoring unit 60 aillustrated in FIG. 33(A) in that one transmitter 76 and one receiver 62are provided. The transmitter 76 transmits an optical signal input viathe power splitter 61 toward a monitoring target (for example, thecontrol unit 20 or the OPS 300). As illustrated in FIG. 67 (A), thetransmitter 76 and the receiver 62 are connected to the transmissionline on the same side in opposite directions.

A monitoring unit 75 b illustrated in FIG. 67(B) includes a powersplitter 61, a plurality of receivers 62-1 to 62-3, a plurality of WDMdevices 63 b-1 to 63 b-2, and a plurality of transmitters 76-1 to 76-3.The monitoring unit 75 b illustrated in FIG. 67(B) is different from themonitoring unit 60 b illustrated in FIG. 33(B) in that the threereceivers 62-1 to 62-3 and the three transmitters 76-1 to 76-3 areprovided instead of the six receivers 62-1 to 62-6. The transmitters76-1 to 76-3 are connected to the WDM device 63 b-1. The receivers 62-1to 62-3 are connected to the WDM device 63 b-2. The WDM device 63 b-1demultiplexes an optical signal branched by the power splitter 61 andoutputs the demultiplexed optical signals to the transmitters 76-1 to76-3. As illustrated in FIG. 67(B), the transmitters 76-1 to 76-3 andthe receivers 62-1 to 62-3 are connected to the transmission line on thesame side in opposite directions.

A monitoring unit 75 c illustrated in FIG. 67(C) includes a powersplitter 61, a receiver 62, a WDM device 63 c, and a transmitter 76. Themonitoring unit 75 c illustrated in FIG. 67(C) is different from themonitoring unit 60 c illustrated in FIG. 33(C) in that the receiver 62and the transmitter 76 are provided instead of the two receivers 62-1and 62-2.

A monitoring unit 75 d illustrated in FIG. 68(A) includes a plurality ofpower splitters 61-1 to 61-3, a plurality of receivers 62-1 to 62-3, aWDM device 63 d, and a plurality of transmitters 76-1 to 76-3. Themonitoring unit 75 d illustrated in FIG. 68(A) is different from themonitoring unit 60 d illustrated in FIG. 34(A) in that the threereceivers 62-1 to 62-3 and the three transmitters 76-1 to 76-3 areprovided instead of the six receivers 62-1 to 62-6. The power splitter61-1 is provided in the transmission line 606-1, and the receiver 62-1and the transmitter 76-1 are connected to the power splitter 61-1. Thepower splitter 61-2 is provided in the transmission line 606-2, and thereceiver 62-2 and the transmitter 76-2 are connected to the powersplitter 61-2. The power splitter 61-3 is provided in the transmissionline 606-3, and the receiver 62-3 and the transmitter 76-3 are connectedto the power splitter 61-3.

A monitoring unit 75 e illustrated in FIG. 68(B) includes a plurality ofpower splitters 61-1 and 61-2, a receiver 62, a plurality of WDM devices63 e-1 and 63 e-2, and a transmitter 76. The monitoring unit 75 eillustrated in FIG. 68(B) is different from the monitoring unit 60 eillustrated in FIG. 34(B) in that the receiver 62 and the transmitter 76are provided instead of the two receivers 62-1 and 62-2. The powersplitter 61-1 is provided in the transmission line 602-1, and thetransmitter 76 is connected to the power splitter 61-1. The powersplitter 61-2 is provided in the transmission line 602-2, and thereceiver 62 is connected to the power splitter 61-2.

A monitoring unit 77 a illustrated in FIG. 69(A) includes a powersplitter 61, a receiver 62, and a transmitter 76. The monitoring unit 77a illustrated in FIG. 69(A) is different from the monitoring unit 60 aillustrated in FIG. 33(A) in that the receiver 62 and the transmitter 76are provided instead of the two receivers 62-1 and 62-2. As illustratedin FIG. 69(A), the transmitter 76 and the receiver 62 are connected tothe transmission line on the same side in the same direction.

A monitoring unit 77 b illustrated in FIG. 69(B) includes a powersplitter 61, a plurality of receivers 62-1 to 62-4, a plurality of WDMdevices 63 b-1 and 63 b-2, a plurality of transmitters 76-1 to 76-4, anda plurality of power splitters 78-1 to 78-4. The monitoring unit 77 billustrated in FIG. 69(B) is different from the monitoring unit 60 billustrated in FIG. 33(B) in that the four receivers 62-1 to 62-4, thefour transmitters 76-1 to 76-4, and the four power splitters 78-1 to78-4 are provided instead of the six receivers 62-1 to 62-6. The powersplitters 78-1 and 78-2 are connected to the WDM device 63 b-1, and thepower splitters 78-3 and 78-4 are connected to the WDM device 63 b-2.The transmitter 76-1 and the receiver 62-1 are connected to the powersplitter 78-1, the transmitter 76-2 and the receiver 62-2 are connectedto the power splitter 78-2, the transmitter 76-3 and the receiver 62-3are connected to the power splitter 78-3, and the transmitter 76-4 andthe receiver 62-4 are connected to the power splitter 78-4. Asillustrated in FIG. 67(B), the transmitters 76-1 to 76-4 and thereceivers 62-1 to 62-4 are connected to the transmission line on thesame side in the same direction as that of the set of the transmitter 76and the receiver 62. In FIG. 69(B), the transmitters 76-2 and 76-4 areprovided outside the monitoring unit 77 b, but may be provided insidethe monitoring unit 77 b.

A monitoring unit 77 c illustrated in FIG. 69(C) includes a powersplitter 61, a plurality of receivers 62-1 and 62-2, a WDM device 63 c,and a plurality of transmitters 76-1 and 76-2. The monitoring unit 77 cillustrated in FIG. 69(C) is different from the monitoring unit 60 cillustrated in FIG. 33(C) in that the two transmitters 76-1 and 76-2 arefurther provided. The monitoring unit 77 c illustrated in FIG. 69(C) hasa different connection relationship from the receivers 62-1 and 62-2 ofthe monitoring unit 60 c illustrated in FIG. 33(C). Specifically, in themonitoring unit 77 c, the receivers 62-1 and 62-2 and the transmitters76-1 and 76-2 are connected to the power splitter 61, the receiver 62-1and the transmitter 76-1 are connected to the transmission line on thesame side, and the receiver 62-2 and the transmitter 76-2 are connectedto the transmission line on the same side.

The number of the power splitters 61, the receivers 62, the WDM devices63, and the transmitters 76 illustrated in FIGS. 67 to 69 is an example,and may be changed according to a situation.

Superimposition of an AMCC signal on a main signal will be described.Since the main signal and the AMCC signal are superimposed, the mainsignal and the AMCC signal are carried by optical signals having thesame wavelength. The main signal is, for example, a signal such as acommon public radio interface (CPRI) such as an on-off keying (OOK)signal of 10 Gbit/s (gigabits per second). The AMCC signal has afrequency that does not overlap, for example, that of an electrical mainsignal, and is superimposed on the main signal with a carrier wavehaving a carrier frequency such as 1 MHz or 500 kHz. A modulation methodis intensity modulation, phase modulation, or the like. In thesuperimposition, for example, an electrical main signal of 10 GHz and anelectrical AMCC signal of 1 MHz are combined by a power combiner andmodulated with the combined signal, and thus the main signal on whichthe AMCC signal is superimposed is generated. The superimposed AMCCsignal can be separated from the main signal.

In the electrical region, the AMCC signal and the main signal usedifferent frequencies. The AMCC signal has a narrower band than the mainsignal. For example, as disclosed in the OITDA standard TP 20 ActiveParts for Optical Transmission-Performance Standard-Optical Transceiverfor GPON (Reference Literature 1:http://www.oitda.or.jp/main/st/TP20-1.pdf) or ITU-T G.958 Appendix I,assuming that the reference of the consecutive identical digit immunityis 72 bits, a lower limit of GE-PON of 1.25 Gbit/s may be sufficientlylower than about 20 MHz, for example, half thereof or sufficientlyhigher than 1.25 GHz, for example, twice thereof, or sufficiently lowerthan 720 kHz of the lower limit of STM-0 of 51.84 Mbit/s of a low-speedsignal, for example, half thereof or sufficiently higher than 51.84 MHz,for example, twice thereof.

As the carrier frequency, another frequency that does not overlap thatof an electrical main signal, such as 500 kHz, may be used, and as amodulation method, another modulation method such as phase modulationmay be used.

In each of the above embodiments, in a case where the subscriber device40 and the control unit 20 have a single-core bidirectional transceiver,the power splitters used for both the uplink and downlink directions maybe connected via the same path of the optical SW 210 in the single-corebidirectional state, or may be separated into two cores and connectedvia the respective paths. In a case where the subscriber device 40 andthe control unit 20 have a double-core bidirectional transceiver, thepower splitters may be bundled in a one-core bidirectional manner andthen connected via the same path of the optical SW 210, or may beconnected via each path in a double-core state. In a case where one ofthe subscriber device 40 and the control unit 20 has a single-corebidirectional transceiver and the other thereof has a bidirectionaltransceiver, the double-core bidirectional directions may be bundled toform a single core and then the power splitters may be connected via thesame path of the optical SW 210, or the single-core bidirectionaldirections may be separated into two cores and then the power splittersmay be connected via the respective paths.

The power splitters used in both uplink and downlink directions aresuitable in a case where wavelength bands that can be used do notoverlap each other in the uplink direction and the downlink direction,such as the 1.3 micron band and the 1.55 micron band. In a case where atleast one the subscriber device 40 and the control unit 20 transmits andreceives an optical signal with a single-core bidirectional opticaltransceiver, they may be connected via a set of ports of the optical SW,or may be connected via two sets of ports and multiplexes signals inopposite directions with a multiplexer/demultiplexer (for example, a WDMdevice or a WDM filter) or a power splitter. Every transmission andreception, different sets of ports may be used for connection, oneoptical transmitter and the other optical receiver may be connected, andthe other optical transmitter and the one optical receiver may beconnected. This is suitable in a case where a double-core opticaltransceiver is used. In this case, different paths may be used on thetransmission side and the reception side.

A plurality of sets may be connected on the transmission side or aplurality of sets may be connected on the reception side. In this case,it is possible to connect or control a plurality of devices orfunctional units. Demultiplexing of connection or control can employ atransmission source, a destination port, a wavelength, a device, afunction unit, or, for example, an identifier for identifying asubscriber device such as a MAC address.

The optical SW, the port, the transmission line, or the connection pointthereof may include a power splitter or a multiplexer/demultiplexerbetween a transmission line connected to another ground or optical SW ora higher network and the optical SW. The multiplexer/demultiplexermultiplexes optical signals having different wavelengths output fromdifferent subscriber devices or the like from a plurality of ports ofthe optical SW, and outputs the multiplexed optical signal to atransmission line connected to another ground or optical SW or a highernetwork. The multiplexer/demultiplexer demultiplexes an optical signaltransmitted from any of another ground, the optical SW, or the highernetwork according to wavelengths, and inputs the demultiplexed opticalsignals to the optical SW from ports corresponding to the wavelengths.In each of the above embodiments, the multiplexer/demultiplexer and thepower splitter have been described. However, in a case wheremultiplexing/demultiplexing is not performed according to wavelengths,the multiplexer/demultiplexer may be a power splitter. In a case whereonly multiplexing or only demultiplexing is performed according towavelengths, only merging multiplexing is performed regardless of awavelength, and only branching is performed regardless of a wavelength,the multiplexer/demultiplexer may be a multiplexer, a demultiplexer, amerging device, and the branching device, respectively.

The power splitter is suitable in a case where an uplink signal and adownlink signal are multiplexed according to, for example, time divisionmultiplexing other than wavelength division multiplexing and a casewhere wavelength bands used by the uplink signal and the downlink signalat least partially overlap. In the latter case, it is sufficient toperform filtering in the optical receiver, the transmission line beforereaching the optical receiver, between the power splitter and thetransmission line, and the like. In a case where a signal passes througha plurality of sections, it is desirable to filter the signal beforebeing multiplexed in order not to influence other signals when thesignal is multiplexed with other signals. In a case where a wavelengthto be filtered by a combination of a multiplexer/demultiplexer or apower splitter and a filter can be changed, the subscriber device maychange the wavelength according to a wavelength to be transmitted andreceived, or the control unit may change the wavelength.

Each configuration described above with reference to FIGS. 1 to 69 maybe modified as follows. In FIGS. 1 to 69 , the monitoring unit 260 ismainly provided at the output of the port of the opposing transmissionline in which the transmission line connected to the subscriber device40 is connected to the port connected to the optical SW. Hereinafter,the monitoring unit 260 is disposed in a transmission line connected tothe subscriber device 40 or between ports connected to the transmissionline. That is, in FIGS. 1 to 69 , the monitoring unit 260 is mainlyprovided in the opposing transmission line connected via the optical SWto the transmission line connecting the subscriber device 40 and theoptical SW. However, in the following modification, the monitoring unit260 is provided in a transmission line connecting the subscriber device40 and the optical SW. The processes in steps S1 and S3 to S6 in theflowchart of FIG. 42 may be performed in other aspects. Step S2 in theflowchart of FIG. 42 is not executed. Hereinafter, another aspect(modification example) of the processes in steps S1 and S3 to S6 will bedescribed. Hereinafter, a portion described as the control unit 301 maybe replaced with the control unit 230 or the control unit 235. A portiondescribed as the monitoring unit 260 may be replaced with the monitoringunit 60, the monitoring unit 65, the monitoring unit 265, or themonitoring unit 267.

FIG. 70 is a diagram illustrating a configuration example in a firstmodification example of the subscriber device 40 and the control unit.In the first modification example, not only an optical signal can betransmitted according to a destination, but also the number of times ofswitching of an optical switch at the time of setting a wavelength ofthe optical signal transmitted from the subscriber device can bereduced. As illustrated in FIG. 38 , the control unit 301 is afunctional unit that instructs another control unit such as the controlunit 230, and the control unit 301 gives an instruction to anothercontrol unit that controls the monitoring unit 260.

In the optical access system 100 (optical communication device), theoptical GW 200 includes the monitoring unit 260 for each input path inthe transmission line 501 between the optical SW 210 and the subscriberdevice 40. That is, the monitoring unit 260 is connected to the port 11on the input side of the optical SW 210. Consequently, the control unit301 is connected to the subscriber device 40 via the monitoring unit260. The control unit 301 does not have to be connected for eachsubscriber device 40 as long as it can be connected to each subscriberdevice 40. For example, even in a case where the control unit 301 issimultaneously connected to a plurality of subscriber devices 40, theoptical SW 21 or the like may be able to select the subscriber device 40that is a connection target, or the optical SW 21 or the like may beable to select the path to be connected, as in the initial connection ofthe PON. Depending on a configuration of the monitoring unit 260, themonitoring unit 260 and the subscriber device 40 do not necessarily havea one-to-one correspondence. For example, a plurality of input paths maycorrespond to one monitoring unit 260. In this case, the monitoring unit260 may monitor an optical signal of the input path according tosettings of switching of the input path. In a case where switching ofthe input path is not set, the monitoring unit 260 may collectivelymonitor optical signals of the plurality of input paths.

As illustrated in FIG. 70 , the control unit 301 is connected to thesubscriber device 40 via the monitoring unit 260. Specifically, at thetime of allocation of a wavelength or the like, since an output of anallocation target device of a wavelength or the like such as thesubscriber device 40 is not connected inside the optical SW 210according to setting by the control unit 301, only the monitoring isexecuted by the monitoring unit 260 installed on the input side of theoptical SW 210 in a state of not being connected to another port of theoptical SW 210. After the wavelength or the like is allocated, a path toanother port of the optical SW 210 is set for the output of theallocation target device of a wavelength or the like such as thesubscriber device 40 according to the setting by the control unit 301.

The optical GW 200 may include the monitoring unit 260 instead of themonitoring unit 260. The optical GW 200 may include, instead of themonitoring unit 260, a power splitter 502 (monitoring unit 260) forbranching and inputting a part of the optical signal from/to thesubscriber device to the control unit 301.

The monitoring unit 260 modulates an optical signal transmitted andreceived by the subscriber device 40 with a control signal, receives apart of the optical signal, multiplexes a signal that is modulated withthe control signal with the optical signal, transfers a part of theoptical signal to the control unit 301, or multiplexes the controlsignal transferred from the control unit 301 with the optical signal. Ina case where some optical signals are received by the monitoring unit260, and the monitoring unit 260 transfers an optical signal on thebasis of some received optical signal, the control unit 301 monitors awavelength or the like of the optical signal of the subscriber device 40on the basis of the optical signal transferred from the monitoring unit260.

In the first modification example of the subscriber device 40 and thecontrol unit 301, a wavelength allocation process (wavelength setting)and a path setting process are executed in this order. Morespecifically, the control unit 301 brings the transmission lineconnected to the subscriber device 40 into a disconnected state in theoptical SW and performs exchange with the subscriber device 40. In aninitial state, the transmission line connected to the subscriber device40 is in a disconnected state in the optical SW, and thus the subscriberdevice 40 is left as it is. At the time of change, basically, thetransmission line connected to the subscriber device 40 is temporarilybrought into a disconnected state in the optical SW. Only in a casewhere there is no influence, the control unit 301 may perform exchangewith the subscriber device 40 while keeping the transmission lineconnected to the subscriber device 40 in a connected state in theoptical SW, or by bringing the transmission line connected to thesubscriber device 40 into a connected state on a changed path in theoptical SW. The optical SW controller 320 switches an output destination(path) of the optical SW 210 after the wavelength change such that thereis no particular influence even if the output destination of the opticalSW 210 is switched.

For example, in a case where the first port and the first wavelength“λ1” are used before switching, and the second port and the secondwavelength “λ2” are used after switching, the following is obtained.

(1) In a case where there is no subscriber device 40 using the firstport and the second wavelength “λ2”:

Switching from the first wavelength “λ1” to the second wavelength “λ2”at the first port has no influence. In this case, it is possible toperform wavelength switching before port switching.

(2) In a case where there is the subscriber device 40 using the firstport and the second wavelength “λ2”:

Switching from the first wavelength “λ1” to the second wavelength “λ2”at the first port has influence. In this case, it is not possible toperform wavelength switching before port switching.

(3) In a case where there is no subscriber device 40 using the secondport and the first wavelength “λ1”:

Switching from the first wavelength “λ1” to the second wavelength “λ2”at the second port has no influence. In this case, it is possible toperform wavelength switching before port switching.

(4) In a case where there is the subscriber device 40 using the secondport and the first wavelength “λ1”:

Switching from the first wavelength “λ1” to the second wavelength “λ2”at the second port has influence. In this case, it is not possible toperform wavelength switching before port switching.

In the above “(1)” and “(3) or (4)”, wavelength switching can beperformed before port switching.

In the above “(1) or (2)” and “(3)”, wavelength switching can beperformed before port switching.

In the above “(2)” and “(4)”, it is not possible to perform wavelengthswitching before port switching.

In the wavelength allocation process, the optical SW controller 320controls the path in the optical SW 210 such that the optical SW 210does not transmit the optical signal of the subscriber device 40 that isa wavelength allocation target.

In a case where there is no particular influence even if an outputdestination of the optical SW 210 is switched before the wavelength isset (before the wavelength is allocated), the optical SW controller 320may switch an output destination of the optical SW 210 before thewavelength is changed. At the time of the wavelength allocation process,a functional unit other than the optical SW 210 may stop transmission ofthe optical signal transmitted from the subscriber device 40. In a casewhere a blocking unit is provided and the optical signal is blocked bythe blocking unit, if the blocking unit blocks the optical signal, theoptical SW controller 320 can basically perform exchange with thesubscriber device 40. As an exception, the blocking unit may not be ableto selectively block an output of the subscriber device 40. This caseis, for example, a case where the blocking unit shares a plurality ofwavelengths and the like (a wavelength, a time, polarizations orthogonalto each other, modes orthogonal to each other, codes orthogonal to eachother, frequencies, cores, core wires, or a combination thereof) withthe subscriber device 40 and the other sharing partner of the subscriberdevice 40 is in operation, a case where a wavelength output at the timeof initial setting is uncertain and there is a possibility that awavelength and the like (a wavelength, a time, polarizations orthogonalto each other, modes orthogonal to each other, codes orthogonal to eachother, frequencies, cores, core wires, or a combination thereof) ofother subscriber devices 40 overlap, a case where outputs at the time ofchanging wavelengths or the like overlap beyond an unallowable time foranother wavelength or the like in operation, and a case where anabnormality occurs and what is output is unknown. In such a case, afterconnection is established without influence (for example, afterreconnection to a non-operating port,), the optical SW controller 320performs exchange with the subscriber device 40. The core is a multicorefiber in which one fiber has a core through which a plurality of opticalsignals propagate. The core wire is each fiber in a cable including aplurality of fibers.

In the wavelength allocation process, the control unit 301 executes thewavelength allocation process on the subscriber device 40 that is awavelength allocation target via the monitoring unit 260. For example,the control unit 301 executes a process of allocating the samewavelength as or a new wavelength different from a wavelength used whenthe abnormality is detected on the subscriber device 40 that is awavelength allocation target.

In the path setting process, the optical switch controller 320 controlsthe optical SW 210 such that an optical signal input from thetransmission line 501 of the subscriber device 40 that is a wavelengthallocation target is output to the port 11 (another port) specifiedaccording to a transfer destination. Here, the transfer destination isspecified according to a subscriber, the subscriber device 40, the port11 of the optical SW 210, a wavelength of an optical signal, acombination of the subscriber device 40 and the wavelength of theoptical signal, a combination of the port 11 and the wavelength of theoptical signal, or the like.

In step S3, in a case where the subscriber device 40 that is awavelength allocation target is connected, the optical SW controller 320causes the transmission line connected to the subscriber device 40 to bedisconnected in the optical SW. In a case where a blocking unit isprovided instead, the blocking unit may block the optical signal. Here,in the optical SW 210, in a case where the transmission line connectedto the port 11-1 connected to the monitoring unit 260 is disconnected toanother port 11 in the optical SW, the control unit 301 maintains thedisconnected state. The subscriber device 40 that is a wavelengthallocation target executes an initialization process before beingconnected to the monitoring unit 260. The subscriber device 40 that is awavelength allocation target may execute the initialization processimmediately after being connected to the monitoring unit 260. In a casewhere a wavelength or the like is set at the time of the initializationprocess, or in a case where at least a part of the initializationprocess such as allocation is executed after reception of an allocationrequest permission in a downlink signal or a downlink signal, at least apart of the initialization process is executed after connection. Thesubscriber device 40 that is a wavelength allocation target transmits aconnection request (register request) by using an optical signal.

In step S4, the control unit 301 receives the connection request fromthe subscriber device 40 that is a wavelength allocation target via themonitoring unit 260. The phrase “via the monitoring unit 260” meansthat, for example, the monitoring unit 260 transfers the optical signalbranched by a combining/branching device to the control unit 301. Forexample, the monitoring unit 260 may include a reception unit, thereception unit may convert an optical signal into an electrical signal,and the reception unit may transfer the electrical signal to aconnection unit. The control unit 301 analyzes the received opticalsignal and determines an initially set wavelength. The control unit 301may analyze the received optical signal and check whether there is aproblem in the optical power.

In step S6, the control unit 301 transmits a wavelength instructionindicating information regarding the wavelength determined (selected) bythe control unit 301 to the subscriber device 40 that is a wavelengthallocation target. The combining/branching device of the monitoring unit260 may merge the optical signal of the control unit 301. The monitoringunit 260 may include a transmission unit, the transmission unit mayconvert an electrical signal into an optical signal, and acombining/branching unit may merge the optical signal. In a case wherethe wavelength instruction is transmitted by using an optical signal viaa wavelength selective element in a path from the monitoring unit 260 tothe subscriber device 40, the wavelength instruction is transmitted tothe subscriber device 40 by using an optical signal having a wavelengthaddressed to the subscriber device 40. The wavelength instruction istransmitted to the subscriber device 40 that is a wavelength allocationtarget via the monitoring unit 260. The monitoring unit 260 outputs theoptical signal input from the control unit 301 to the subscriber device40. The optical signal indicating the wavelength instruction may bebranched in the middle of the transmission line 501. In a case where atransmission wavelength is set in the wavelength instruction, thesubscriber device 40 that is a wavelength allocation target sets thetransmission wavelength of the optical signal of the optical transceiveraccording to the wavelength instruction.

In step S7, in a case where a notification signal is transmitted byusing the optical signal, the subscriber device 40 transmits thenotification signal for notifying that the wavelength is set to thecontrol unit 301 via the monitoring unit 260 by using the optical signalhaving the wavelength designated in the wavelength instruction. Thecontrol unit 301 checks whether or not the designated wavelength iscorrectly set on the basis of the notification signal. The control unit301 may check whether the output power of the optical signal issufficient on the basis of the notification signal.

In step S8, the control unit 301 transmits optimum connectioninformation (path information) of each port 11 of the optical SW 210 tothe optical SW 210 according to a transmission destination (destination)of the optical signal of the subscriber device 40. The optical SW 210sets an uplink port and a downlink port of the subscriber device 40 onthe basis of the connection information.

FIG. 71 is a flowchart illustrating an initial setting process of theoptical access system according to the first modification example of thesubscriber device 40 and the optical GW control unit 302. The referencesigns illustrated in FIG. 71 are similar to the reference signsillustrated in FIG. 42 . A port is connected between step S1 and step S3illustrated in FIG. 71 . In step S4, the present invention is notlimited to the AMCC. The main signal is dripped, and the control unit301 and the input monitoring unit autonomously check the main signal. Instep S7, the control unit 301, the input monitoring unit, the outputmonitoring unit, the communication unit, or the subscriber device 40autonomously performs checking.

As described above, in the first modification example of the subscriberdevice 40 and the control unit 301, the optical SW 210 outputs theoptical signal input from any one of the plurality of transmission lines501 to another transmission line 501 among the plurality of transmissionlines 501. The monitoring unit 260 relays the optical signal betweenanother control unit that receives an instruction from the control unit301 and the subscriber device 40 in the transmission line 501 on theside where the optical signal transmitted from the subscriber device 40is input to the optical SW 210. The monitoring unit 260 relays theoptical signal between the subscriber device 40 and the optical SW 210in the transmission line 501 on the side where the optical signal isinput to the optical SW 210. The control unit 301 allocates a wavelengthto the optical signal of the subscriber device 40 via the monitoringunit 260. After the wavelength is allocated to the optical signal of thesubscriber device 40, the control unit 301 controls the optical SW 210such that the optical signal input to the optical SW 210 via thetransmission line 501 on the input side is output to anothertransmission line 501. The optical GW 200 may include a first optical SW210 and a second optical SW 210 cascade-connected to the first opticalSW 210. Before the wavelength is allocated to the optical signal of thesubscriber device 40, the optical SW controller 320 may control theoptical SW 210 such that the optical signal input to the optical SW 210via the transmission line 501 on the input side is not output to anothertransmission line 501.

Consequently, in the first modification example of the subscriber device40 and the control unit 301, it is possible not only to transmit anoptical signal according to a destination but also to reduce the numberof times of switching of the optical switch at the time of setting awavelength of the optical signal transmitted from the subscriber device.

Hereinafter, a second modification example will be described.

Each configuration described above with reference to FIGS. 1 to 69 maybe modified as follows.

In this case, for example, in the monitoring unit illustrated in FIGS.33, 67, and 69 , when viewed from the direction in which the opticalsignal is input; in the monitoring unit illustrated in FIGS. 34(A) and68(A), the blocking unit is provided at the subsequent stage of thepower splitter 61 in a case where the blocking unit is individuallyprovided and is provided at the subsequent stage of the WDM device 63 din a case where the blocking unit is collectively provided for aplurality of wavelengths; in the monitoring unit illustrated in FIGS.34(B) and 68 (B), in a case where the blocking unit is separatelyprovided in uplink and downlink paths, the blocking unit is providedbetween the power splitter and the WDM device 63 e-1 at the subsequentstage thereof in the uplink path and is provided between the powersplitter and WDM device 63 e-2 at the subsequent stage thereof in thedownlink path, and in a case where the other direction may be blocked atthe time of setting one direction, the blocking unit is provided thesubsequent stage of the WDM device 63 e-1 in the uplink path and isprovided at the subsequent stage of the WDM device 63 e-2 in thedownlink path; in the monitoring unit illustrated in FIG. 35 , theblocking unit is provided at the preceding stage or the subsequent stage(also used as a modulator) of the modulator 64; and in the monitoringunit illustrated in FIG. 36 , the blocking unit is provided at thepreceding stage of the WDM devices 63 g-1 and 63 g-2 and at thepreceding stage or the subsequent stage (also used as a modulator) ofthe modulator 64.

The processes in steps S1 to S8 in the flowchart of FIG. 42 may beperformed in another aspect. Hereinafter, another aspect (modificationexample) of the processes in steps S1 to S8 will be described.

FIG. 72 is a diagram illustrating a configuration example in a secondmodification example of the subscriber device 40 and the control unit.In the second modification example, not only an optical signal can betransmitted according to a destination, but also the number of times ofswitching of the optical switch at the time of setting a wavelength ofthe optical signal transmitted from the subscriber device can be reducedin some cases.

In the optical access system 100 (optical communication device), theoptical GW 200 includes a monitoring unit for each output path in thetransmission line 503 on the output side of the optical SW 210. That is,the monitoring unit is connected to the port 11 on the output side ofthe optical SW 210. Consequently, the wavelength controller 310 isconnected to the subscriber device 40 via the monitoring unit. Dependingon a configuration of the monitoring unit, the monitoring unit and theoutput path do not necessarily correspond to each other on a one-to-onebasis. For example, in a case where the target subscriber device 40 canbe selected as in the initial connection of the PON, or in a case wherea path to be connected via the optical SW 210 or the like can beselected, a plurality of output paths and one monitoring unit maycorrespond to each other. In this case, the monitoring unit may monitoran optical signal on the output path according to setting of switchingof the output paths. In a case where the switching of the output pathsis not set, the monitoring unit may collectively monitor optical signalson the plurality of output paths.

As illustrated in FIG. 72 , the control unit is connected to thesubscriber device 40 via the monitoring unit. Specifically, at the timeof wavelength allocation, an output of a wavelength allocation targetdevice such as the subscriber device 40 is input to another port in theoptical SW 210 according to setting by the control unit. However, theoutput is only monitored by the monitoring unit installed on the outputside, and transmission through the transmission line 503 is blocked bythe blocking unit 263. The blocking is canceled after the allocation.

The optical GW 200 may include a monitoring unit instead of themonitoring unit. Instead of the monitoring unit, the optical GW 200 mayinclude a power splitter 502 (monitoring unit) for branching andinputting some optical signals from/to the subscriber device to thecontrol unit.

The monitoring unit transfers some optical signals transmitted andreceived by the subscriber device 40 to the control unit. The wavelengthcontroller 310 monitors a wavelength or the like of an optical signal ofthe subscriber device 40 on the basis of an optical signal transferredfrom the monitoring unit.

The monitoring unit includes a blocking unit 263. The blocking unit 263can block transmission of an optical signal in the transmission line503. The blocking unit 263 blocks transmission of the optical signalbefore the path setting process and the wavelength allocation process(wavelength setting) are performed under the control of the wavelengthcontroller 310. The blocking unit 263 cancels the blocking of thetransmission of the optical signal after the path setting process andthe wavelength allocation process are performed.

For example, an optical switch may be used as the blocking unit 263.Alternatively, for example, a semiconductor optical amplifier (SOA) maybe used as the blocking unit 263. In this case, an amplification factorin the semiconductor optical amplifier is set to a value (for example,−10 dB) equal to or less than an extinction ratio of the modulator in acase where a single path is provided or outputs of the subscriberdevices 40 are combined, a value (for example, −25 dB in a case of 32)smaller by several outputs in a case where a plurality of outputs arecombined, and −35 dB or the like in a case where there is a differenceof 10 dB due to perspective difference or the like, and thus thetransmission of the optical signal is blocked.

In a case where a disposition position of the blocking unit 263 is setand changed, for example, in both uplink and downlink directions, theblocking unit is preferably disposed at a position at a subsequent stageof multiplexing or merging of optical signals. On the other hand, in acase where a disposition position of the blocking unit 263 is set andchanged separately in the uplink and downlink directions, for example,the blocking unit is preferably disposed at a position at a subsequentstage of demultiplexing or branching of an optical signal. In a casewhere a combination of a plurality of outputs is blocked, the number ofblocking units 263 is reduced. On the other hand, in a case where adivided output is blocked, setting can be individually performed, andthe degree of freedom is increased.

The blocking unit 263 may be a functional unit or a device providedoutside the monitoring unit. In a case where an extinction ratio of themodulator is high enough not to affect other optical signals, themodulator may also serve as the blocking unit 263.

Hereinafter, blocking transmission of an optical signal may be simplyreferred to as “blocking”. Hereinafter, canceling blocking oftransmission of an optical signal may be simply referred to as “blockingcancelation”.

In the first modification example of the subscriber device 40 and thecontrol unit, the blocking, the path setting process, the wavelengthallocation process (wavelength setting), and the blocking cancellationare performed in this order. With such an order, even if the pathsetting process is performed, an optical signal before wavelengthsetting is not transmitted to the outside of the optical GW 200 via thetransmission line 503.

In a case where an optical signal is blocked by the blocking unit, ifthe blocking unit blocks the optical signal, the optical SW controller320 can basically perform exchange with the subscriber device 40. As anexception, the blocking unit may not be able to selectively block anoutput of the subscriber device 40. This case is, for example, a casewhere the blocking unit shares a plurality of wavelengths and the like(a wavelength, a time, polarizations orthogonal to each other, modesorthogonal to each other, codes orthogonal to each other, frequencies,core wires (cores), or a combination thereof) with the subscriber device40 and the other sharing partner of the subscriber device 40 is inoperation, a case where a wavelength output at the time of initialsetting is uncertain and there is a possibility that a wavelength andthe like (a wavelength, a time, polarizations orthogonal to each other,modes orthogonal to each other, codes orthogonal to each other,frequencies, core wires (cores), or a combination thereof) of othersubscriber devices 40 overlap, a case where outputs at the time ofchanging wavelengths or the like overlap beyond an allowable time foranother wavelength or the like in operation, and a case where anabnormality occurs and what is output is unknown. In such a case, afterconnection is established without influence (for example, afterreconnection to a non-operating port,), the optical SW controller 320performs exchange with the subscriber device 40.

As an exception, when there is no influence even if it is not blocked,blocking may not be performed. Alternatively, it may be configured to beconnected to an output port that is not affected even if the output portis not blocked, and set by a monitoring unit of the output port.

In the path setting process, the optical switch controller 320 controlsa path in the optical SW 210 such that the subscriber device 40 that isa wavelength allocation target is connected to the port 11 (anotherport) other than the port 11 connected to the monitoring unit of thesubscriber device 40 that is a wavelength allocation target. Forexample, the optical switch controller 320 controls the optical SW 210to output an optical signal input from the transmission line 501 of thesubscriber device 40 that is a wavelength allocation target to the port11 (another port) specified according to a transfer destination. Here,the transfer destination is specified according to a subscriber, thesubscriber device 40, the port 11 of the optical SW 210, a wavelength ofan optical signal, a combination of the subscriber device 40 and thewavelength of the optical signal, a combination of the port 11 and thewavelength of the optical signal, or the like.

In the wavelength allocation process, the wavelength controller 310executes the wavelength allocation process on the subscriber device 40that is a wavelength allocation target. For example, the wavelengthcontroller 310 executes a process of allocating the same wavelength asor a new wavelength different from a wavelength used when theabnormality is detected on the subscriber device 40 that is a wavelengthallocation target.

FIG. 73 is a flowchart illustrating an initial setting process of anoptical access system according to a second modification example. Adescription will focus on differences from the initial setting processillustrated in the flowchart of FIG. 42 .

In step S2, the control unit controls the monitoring unit installed onthe output side of the optical SW 210, and causes the blocking unit 263to block transmission in the transmission line 503 such that the opticalsignal of the subscriber device 40 is not transmitted through thetransmission line 503. The optical SW controller 320 executes a pathsetting process in the optical SW 210.

In step S3, the wavelength controller 310 receives a connection requestfrom the subscriber device 40 that is a wavelength allocation target.The subscriber device 40 that is a wavelength allocation target executesan initialization process before being connected to the optical SW 210.The subscriber device 40 that is a wavelength allocation target mayexecute an initialization process immediately after being connected tothe optical SW 210. In a case where a wavelength or the like is set atthe time of the initialization process, or in a case where at least apart of the initialization process such as allocation is executed afterreception of an allocation request permission in a downlink signal or adownlink signal, at least a part of the initialization process isexecuted after connection. The subscriber device 40 that is a wavelengthallocation target transmits a connection request (register request) byusing an optical signal.

In step S4, the wavelength controller 310 receives the connectionrequest from the subscriber device 40 that is a wavelength allocationtarget via the monitoring unit. The phrase “via the monitoring unit”means that, for example, the monitoring unit transfers an optical signalbranched by the combining/branching device to the wavelength controller310. For example, a state of an electrical signal may be used (themonitoring unit includes a receiving unit, the receiving unit convertsan optical signal into an electrical signal, and the receiving unittransfers the electrical signal to the connection unit). The wavelengthcontroller 310 analyzes the optical signal received by the monitoringunit and determines an initially set wavelength. The wavelengthcontroller 310 may analyze the received optical signal and check whetherthere is a problem in the optical power.

In step S6, the wavelength controller 310 (control unit) transmits awavelength instruction indicating information regarding the wavelengthdetermined (selected) by the control unit 301 to the subscriber device40 that is a wavelength allocation target. The optical signal of thewavelength controller 310 may be merged by the combining/branchingdevice of the monitoring unit. The monitoring unit may include atransmission unit, the transmission unit may convert an electricalsignal into an optical signal, and a combining/branching unit may mergethe optical signal. In a case where the wavelength instruction istransmitted by using an optical signal, the wavelength instruction istransmitted to the subscriber device 40 by using an optical signalhaving a wavelength addressed to the subscriber device 40. Thewavelength instruction is transmitted to the subscriber device 40 thatis a wavelength allocation target via the monitoring unit. Themonitoring unit outputs the optical signal input from the wavelengthcontroller 310 to the subscriber device 40. The optical signalindicating the wavelength instruction may be branched in the middle ofthe transmission line 501. In a case where a transmission wavelength isset in the wavelength instruction, the subscriber device 40 that is awavelength allocation target sets the transmission wavelength of theoptical signal of the optical transceiver according to the wavelengthinstruction.

In step S7, in a case where a notification signal is transmitted byusing an optical signal, the subscriber device 40 transmits, to thewavelength controller 310 via the monitoring unit, the notificationsignal for notifying that the wavelength is set by using the opticalsignal having the wavelength designated in the wavelength instruction.The wavelength controller 310 checks whether or not the designatedwavelength is correctly set on the basis of the notification signal. Thewavelength controller 310 may check whether the output power of theoptical signal is sufficient on the basis of the notification signal.

In step S8, in a case where the designated wavelength is correctly set,the wavelength controller 310 controls the blocking unit 263 to cancelthe blocking. Consequently, communication between the subscriber device40 that is a wavelength allocation target and the subscriber device 40that is a communication destination is started.

As described above, in the second modification example of the subscriberdevice 40 and the control unit, the optical SW 210 outputs an opticalsignal input from any one transmission line 501 among the plurality oftransmission lines 501 to any one transmission line 503 among theplurality of transmission lines 503. The monitoring unit relays anoptical signal between the optical SW 210 and the subscriber device 40that is a communication destination in the transmission line 503 on theside where the optical signal transmitted from the subscriber device 40is output from the optical SW 210. The wavelength controller 310controls the blocking unit 263 to block transmission of the opticalsignal output from the monitoring unit. After the blocking by theblocking unit 263 is performed, the optical SW controller 320 executes apath setting process of the optical signal in the optical SW 210. Next,the wavelength controller 310 allocates a wavelength to the opticalsignal of the subscriber device 40 on the basis of the monitoring resultfrom the monitoring unit. Next, the wavelength controller 310 controlsthe blocking unit 263 to cancel the blocking of the transmission of theoptical signal output from the monitoring unit. As described above, thecontrol unit causes the blocking unit 263 to perform blocking before thewavelength is allocated, and thus prevents the optical signal input fromthe transmission line 501 to the optical SW 210 from being output to theother transmission line 503. After the blocking is performed, thecontrol unit executes the path setting process and the wavelengthallocation process (wavelength setting) in this order. The control unitcauses the blocking unit 263 to perform blocking cancelation after thewavelength is allocated such that the optical signal input from thetransmission line 501 to the optical SW 210 is output to the othertransmission line 503. The optical GW 200 may include the first opticalSW 210 and the second optical SW 210 cascade-connected to the firstoptical SW 210.

Consequently, in the second modification example of the subscriberdevice 40 and the control unit, it is possible not only to transmit anoptical signal according to a destination but also to reduce the numberof times of switching of the optical switch at the time of setting awavelength of the optical signal transmitted from the subscriber devicein some cases.

Although the wavelength change process performed by the subscriberdevice 40 requesting wavelength change has been described above, thesame applies to a wavelength change process performed by the controlunit 20 on the basis of monitoring information or the like.

The control signal is exchanged between the control unit 20 and thesubscriber device 40. For example, the subscriber device 40 transmits aconnection request to the control unit 20, and the control unit 20transmits a control signal to the subscriber device 40. For example, thecontrol unit 20 allocates a wavelength used for communication by thesubscriber device 40.

The control signal may be monitored by the monitoring unit 60 andexchanged between the monitoring unit 60 and the subscriber device 40and between the monitoring unit 60 and the control unit 20.

The wavelength controller 310 and the optical SW controller 320 may beimplemented by using one information processing device, or may beimplemented by using a plurality of information processing devicescommunicatively connected via a network.

As illustrated in FIG. 74 , the optical GW may be configured as a device(an optical communication device of the present invention) including anyor all of the OPS 300 or the control unit 20, the optical SW, themonitoring unit, the electrical processing unit, the return transmissionline, the combining/branching device (power splitter), and themultiplexer/demultiplexer (the WDM device or the WDM filter).

In each of the above embodiments, allocation of a wavelength to thesubscriber device 40 has been described as an example. However, awavelength and the like that are a wavelength, a time, a polarizationorthogonal to each other, modes orthogonal to each other, codesorthogonal to each other, frequencies, cores, core wires, or acombination thereof may be allocated. For example, the same applies to amultiplexer/demultiplexer in a case where a time, a polarization, amode, a code, a core, or a core wire is allocated if themultiplexer/demultiplexer is replaced with a combination of acombining/branching device and a delay line, a polarization modecoupler, a mode coupler, a decoder/encoder, an inter-corecombining/branching device, an inter-core wire combining/branchingdevice, or the like.

The control units 20, 230, and 235, the monitoring units 260, 265, and267, the wavelength controller 310, and the optical SW controller 320described above may include a CPU, a memory, an auxiliary storagedevice, and the like connected via a bus, and may realize some or all ofthe above-described functions by executing a program. Some or all of thefunctions of the control units 20, 230, and 235, the monitoring units260, 265, and 267267, the wavelength controller 310, and the optical SWcontroller 320 may be realized by using hardware such as ASIC, PLD, orFPGA. The program for the control units 20, 230, and 235, the monitoringunits 260, 265, and 267, the wavelength controller 310, and the opticalSW controller 320 may be recorded in a computer-readable recordingmedium. The computer-readable recording medium is, for example, aportable medium such as a magneto-optical disk, a ROM, or a CD-ROM, or astorage device such as a hard disk built in a computer system. Theprogram may be transmitted via an electrical communication line.

Although the embodiments of the present invention have been described indetail with reference to the drawings so far, specific configurationsare not limited to these embodiments, and include designs and the likewithout departing from the spirit of the present invention.

INDUSTRIAL APPLICABILITY

The present invention is applicable to an optical access systemtechnique using an optical switch.

REFERENCE SIGNS LIST

-   -   1 Optical communication system    -   10, 10 a, 10 b, 10 c, 10 d, 10 e, 10 f, 10 g, 34, 95 a-1, 95        a-2, 95 b-1, 95 b-2, 96 a-1, 96 a-2, 96 b-1, 96 b-2, 210, 211,        212 a, 212 b, 212 c, 1001, 1002, 1003, 1004, 1005, 1006, 1007,        1008, 1009 a, 1009 b, 1010-1 to 1010-4 Optical switch    -   11-1, 11-1-1 to 11-1-P, 11-2, 11-2-1 to 11-2-Q Port    -   20 Control unit    -   21, 41, 411, 412 Optical transceiver    -   22, 42, 237 Optical transmitter    -   23, 43, 232, 236, 262 Optical receiver    -   25 Wavelength controller    -   26, 320 Optical SW controller    -   30 Optical communication network    -   31 WDM access ring network    -   32-1 to 32-r Add/drop node    -   33 Demultiplexing unit    -   35 Multiplexing unit    -   40, 40-1 to 40-M, 40 a-1 to 40 a-3, 40 b-1 to 40 b-3, 40 c-1 to        40 c-3, 40 a-1-1, 40 a-1-2, 40-p-1 to 40-p-Np, 40-p-N, 40-p to        40-(p+N) Subscriber device    -   46-1, 46-3 User    -   46-2 Mobile base station    -   50, 50-1, 50-2, 50-1-p to 50-1-(p+N), 50-1-p 1 to 50-1-pN,        50-1-p-1 to 50-p-Np, 50-2-1 to 50-2-q, 50-2-(N−1), 50-2-N,        50-2-q-1 to 50-2-q-N, 50-2-(1+N), 53, 54 a, 54 b, 54 c, 54 d,        92, 93-1 to 93-N, 501, 503, 504, 511, 512, 521, 522, 531, 533,        534, 540, 541, 542, 543-1, 543-2, 544, 545, 546, 547, 548, 549,        551, 551 a, 552, 552 b, 555, 560, 561, 562, 563, 570, 571, 572,        573, 574, 575, 581, 582, 583, 584, 585, 586, 587, 588, 589        Transmission line    -   51, 73 Return transmission line    -   55, 55-1, 55-2, 55-p, 55-(p+1), 56, 57 a, 57 b, 61, 66, 69, 71,        72, 251, 251 a, 251 b, 252, 252 b, 254, 258, 259, 270, 271, 272,        273, 502, 507 Power splitter    -   58, 59 Distribution unit    -   60, 60 a to 60 h, 65 Monitoring unit    -   67, 68, 80, 80 a, 80 b, 80 c, 81, 89, 97 WDM device    -   82 a-1 to 82 a-n, 82 b-1 to 82 b-m, 241, 247, 458 Multiplexer    -   83 a-1 to 83 a-n, 83 b-1 to 83 b-m, 242, 248, 457 Demultiplexer    -   85, 610 O/E conversion unit    -   86, 620 Processing execution unit    -   87, 630 E/O conversion unit    -   88 Storage unit    -   90, 91 Multiplex communication transmission line    -   100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112,        113, 114, 115, 116, 117 Optical access system    -   200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 2010, 2011,        2012, 2013, 2014, 2015, 2016 Optical gateway    -   220, 238, 243, 244, 245, 249, 256, 257 Wavelength        multiplexer/demultiplexer    -   230, 235 Control unit    -   231, 261 Wavelength demultiplexer    -   233, 269 Wavelength tunable transmitter    -   250, 250 a, 250 b, 253, 255 Branching unit    -   260, 265 Monitoring unit    -   263 Blocking unit    -   266 Wavelength tunable optical receiver    -   267 Monitoring unit    -   268 Wavelength tunable receiver    -   300 Operation system    -   301 Optical GW control unit    -   310 Control unit    -   350 Management database    -   452 Variable wavelength receiver    -   453 Wavelength tunable filter    -   459, 459 a to 459 e WDM filter    -   84, 600 Electrical processing unit    -   861 Processor    -   862 Accelerator

1. An optical communication device comprising: an optical switch thatoutputs an optical signal input from one of a plurality of transmissionlines to another transmission line among the plurality of transmissionlines; a monitoring unit that relays an optical signal in a transmissionline on a side where the optical signal is output from the opticalswitch; a blocking unit that blocks transmission of an optical signaloutput from the monitoring unit; a wavelength controller that allocatesa wavelength and the like that are a wavelength, a time, a polarization,a mode, a code, a frequency, a core, a core wire, or a combinationthereof to an optical signal of a subscriber device via the monitoringunit; and an optical switch controller that controls the optical switchsuch that the optical signal input from the transmission line to theoptical switch is output to the another transmission line, and cancelsthe blocking by the blocking unit.
 2. The optical communication deviceaccording to claim 1, wherein the optical switch controller causes theblocking unit to perform the blocking before the wavelength and the likeare allocated, and cancels the blocking by the blocking unit after thewavelength is allocated.
 3. The optical communication device accordingto claim 1, wherein the blocking unit includes an optical switchdifferent from the optical switch or a semiconductor optical amplifier.4. An optical communication device comprising: a first optical switchthat outputs an optical signal input from one of a plurality oftransmission lines to another transmission line among the plurality oftransmission lines; a second optical switch that is cascade-connected tothe first optical switch; a monitoring unit that relays an opticalsignal in a transmission line on a side where the optical signal isoutput from the first optical switch or the second optical switch; ablocking unit that blocks transmission of an optical signal output fromthe monitoring unit; a wavelength controller that allocates a wavelengthand the like that are a wavelength, a time, a polarization, a mode, acode, a frequency, a core, a core wire, or a combination thereof to anoptical signal of a subscriber device via the monitoring unit; and anoptical switch controller that controls the first optical switch and thesecond optical switch such that the optical signal input from thetransmission line to the first optical switch is output to the anothertransmission line, and cancels the blocking by the blocking unit.
 5. Theoptical communication device according to claim 4, wherein the opticalswitch controller causes the blocking unit to perform the blockingbefore the wavelength and the like are allocated, and cancels theblocking by the blocking unit after the wavelength is allocated.
 6. Anoptical communication system comprising: a plurality of subscriberdevices; and the optical communication device according to claim
 1. 7.An optical communication method executed by an optical communicationdevice, comprising: an optical switch step of outputting an opticalsignal input from one of a plurality of transmission lines to anothertransmission line among the plurality of transmission lines; amonitoring step of relaying an optical signal in a transmission line ona side where the optical signal is output from the optical switch; ablocking step of blocking transmission of an optical signal output inthe monitoring step; a wavelength control step of allocating awavelength and the like that are a wavelength, a time, a polarization, amode, a code, a frequency, a core, a core wire, or a combination thereofto an optical signal of a subscriber device; and an optical switchcontrol step of controlling the optical switch such that an opticalsignal input from the transmission line to the optical switch is outputto the another transmission line, and canceling the blocking.